- 0 A.D. (C, C++, JavaScript, GPL-2.0, beta)
- 1oom (C, GPL-2.0, mature)
- 2009scape (Java, Kotlin, AGPL-3.0, mature)
- 3DWorld (C++, GPL-3.0, mature)
- 4D Maze Game (Java, Public domain, mature, inactive since 2008)
- 4D-TRIS (C, GPL-2.0, mature, inactive since 2012)
- Abe's Amazing Adventure (C, GPL-2.0, mature, inactive since 2005)
- AdaGate (Ada, GPL-3.0, mature)
- Airstrike (C, GPL-2.0, beta, inactive since 2014)
- Aleph One (C++, Lua, GPL-3.0, mature)
- Alex the Allegator 4 (C, GPL-2.0, mature, inactive since 2003)
- alive (C++, MIT, beta)
- Ambermoon.net (C#, GPL-3.0, mature)
- Ambrose3D (C++, zlib, beta, inactive since 2007)
- AndEngine (Java, Apache-2.0, mature, inactive since 2013)
- AnKi 3D engine (C++, 3-clause BSD, beta)
- Annex: Conquer the World (Lua, GPL-3.0, mature, inactive since 2014)
- AntiChess (Java, MIT, beta, inactive since 2003)
- Anura (C, C++, zlib, mature)
- Arcane-Engine (C++, MIT, beta)
- Ares Dogfighter (Java, GPL-3.0, beta, inactive since 2016)
- Armory (Haxe, Python, zlib, mature)
- AssaultCube (C, C++, Custom, mature, inactive since 2018)
- Atomic Tanks (C++, C, GPL-2.0, mature, inactive since 2016)
- Augustus (C, C++, AGPL-3.0, mature)
- Aussenposten (JavaScript, MIT, beta, inactive since 2015)
- Azimuth (C, GPL-3.0, mature)
- Battle Tanks (C++, GPL-2.0, mature, inactive since 2009)
- Berusky (C++, GPL-3.0, mature)
- Biniax (C, zlib, mature, inactive since 2012)
- Bitfighter (C, C++, GPL-2.0, mature)
- Black Shades (C, GPL-3.0, mature)
- Blackvoxel (C++, GPL-3.0, mature)
- Bladecoder Adventure Engine (Java, Apache-2.0, mature)
- Blitwizard (C, C++, Lua, zlib, beta, inactive since 2015)
- Blobby Volley 2 (C++, GPL-2.0, mature, inactive since 2017)
- Blobwars: Metal Blob Solid (C++, C, GPL-2.0, mature)
- Block Attack - Rise of the Blocks (C++, GPL-2.0, mature)
- BlockOut II (C++, GPL-2.0, mature, inactive since 2014)
- BomberClone (C, GPL-2.0, beta, inactive since 2010)
- Bombermaaan (C++, GPL-3.0, mature, inactive since 2010)
- Brain Workshop (Python, GPL-2.0, mature, inactive since 2011)
- BRIQUOLO (C++, GPL-3.0, mature, inactive since 2008)
- Brogue (C, AGPL-3.0, mature)
- Brutal Chess (C++, GPL-2.0, beta, inactive since 2007)
- BStone (C++, GPL-2.0, mature)
- BZFlag (C++, LGPL-2.1, MPL-2.0, mature)
- C-Dogs SDL (C, GPL-2.0, mature)
- CaesarIA (C++, JavaScript, C, GPL-3.0, beta)
- Cannon Smash (C++, GPL-2.0, beta, inactive since 2003)
- Canta (Python, GPL-3.0, beta, inactive since 2011)
- Caph (C, GPL-3.0, mature, inactive since 2010)
- Carnage3D (C++, C, MIT, beta)
- Cart Life (AGS Script, Custom, mature, inactive since 2014)
- Cartographer (GDScript, Apache-2.0, mature)
- Cat Mother Dead Justice (C++, 3-clause BSD, GPL-2.0, beta, inactive since 2003)
- Cataclysm: Dark Days Ahead (C++, CC-BY-SA-3.0, mature)
- CatacombGL (C++, GPL-3.0, beta)
- CaveExpress (C, JavaScript, GPL-3.0, mature)
- CavePacker (JavaScript, C, C++, Lua, GPL-3.0, mature)
- Childsplay (Python, GPL-3.0, mature)
- Chocolate Doom (C, GPL-2.0, mature)
- Chronoshift (C++, GPL-2.0, beta)
- Chunk Stories (Kotlin, Java, LGPL-3.0, beta)
- Circus Linux! (C, GPL-2.0, mature, inactive since 2000)
- Citybound (Rust, JavaScript, AGPL-3.0, beta)
- ClanLib (C, C++, zlib, mature)
- Classic RBDoom 3 BFG (C, C++, GPL-3.0, mature)
- ClassiCube (C, 3-clause BSD, mature)
- Clonepoint (C++, GPL-3.0, beta)
- Colditz Escape (C, GPL-3.0, mature)
- Combat Simulator Project (C++, GPL-2.0, beta, inactive since 2010)
- Commander Genius (C, C++, GPL-2.0, mature)
- CoTerminalApps (Ada, GPL-3.0, mature)
- Crack Attack! (C++, GPL-2.0, mature, inactive since 2005)
- Craft (C, Python, MIT, mature, inactive since 2017)
- CrossUO (C, C++, GPL-3.0, mature)
- Crystal Space 3D SDK (C, C++, LGPL-2.1, mature, inactive since 2015)
- Cultivation (C++, Public domain, mature, inactive since 2010)
- Curse of War (C, C++, GPL-3.0, mature, inactive since 2014)
- Cytadela (C++, GPL-3.0, beta, inactive since 2013)
- D-Fend Reloaded (Pascal, GPL-3.0, mature, inactive since 2015)
- D2X-XL (C++, Custom, GPL-2.0, mature, inactive since 2015)
- Daedalus (C++, GPL-2.0, mature, inactive since 2018)
- Daggerfall Unity (C#, MIT, mature)
- DarkPlaces (C, GPL-2.0, mature, inactive since 2014)
- Dave Gnukem (C++, GPL-2.0, mature)
- DDraceNetwork (C, C++, zlib, beta)
- Deer Portal (C++, zlib, beta)
- Defendguin (C, GPL-2.0, mature, inactive since 2009)
- DeSmuME (C, C++, GPL-2.0, mature, inactive since 2015)
- Destination Sol (Java, Apache-2.0, mature)
- dhewm3 (C, C++, GPL-3.0, mature)
- Digital: A Love Story (Ren'Py, Python, CC-BY-NC-SA-3.0, mature)
- dim3 (C, MIT, beta, inactive since 2014)
- DirectPython (C++, 2-clause BSD, beta, inactive since 2007)
- DirectX12GameEngine (C#, MIT, beta)
- Do It Yourself Doom With SDL (C++, MIT, beta)
- Domination (Java, GPL-3.0, mature)
- donut (C, C++, GPL-3.0, beta)
- Doom Legacy (C++, GPL-2.0, mature)
- DOOM Retro (C, C++, GPL-3.0, mature)
- Doom64EX (C, C++, GPL-2.0, mature)
- Doomsday Engine (C, C++, GPL-2.0, GPL-3.0, LGPL-3.0, mature)
- Dope Wars (C, GPL-2.0, mature, inactive since 2013)
- DreamChess (C, GPL-3.0, beta)
- DRL (Lua, Pascal, GPL-2.0, mature)
- Duck Marines (Lua, zlib, mature, inactive since 2016)
- Duel Commander (C, GPL-3.0, beta, inactive since 2009)
- Dune II - The Maker (Java, MIT, beta)
- Dungeon (Java, 3-clause BSD, mature)
- Dust Racing 2D (C, C++, GPL-3.0, mature)
- DwarfCorp (C#, MIT, mature)
- DXX-Rebirth (C, C++, Python, GPL-3.0, Custom, mature)
- EasyRPG Editor (C++, GPL-3.0, mature)
- Eat The Whistle (C, ?, mature, inactive since 2017)
- ECWolf (C++, GPL-2.0, LGPL-2.1, zlib, MIT, IJG, Public domain, mature)
- EDGE (C++, C, GPL-2.0, mature)
- EdisonEngine (C++, Python, LGPL-3.0, beta)
- ElonaFoobar (C++, Lua, MIT, mature)
- Emilia Pinball (C++, GPL-2.0, beta)
- EmptyEpsilon (C, C++, Lua, GPL-2.0, mature)
- Enigma (C, C++, GPL-2.0, mature)
- Escape Towards The Unknown (C, GPL-2.0, beta, inactive since 2016)
- Esenthel Engine (C, C++, Custom, beta)
- ET: Legacy (C, C++, Lua, GPL-3.0, mature)
- Etterna (C, C++, Lua, MIT, beta)
- ezEngine (C++, JavaScript, MIT, mature)
- ezQuake (C, C++, GPL-2.0, mature)
- F-1 Spirit (C++, ?, beta, inactive since 2009)
- Falcon's Eye (C, NetHack General Public License, mature, inactive since 2004)
- Falltergeist (C++, GPL-3.0, beta)
- Faur (C, Python, C++, GPL-3.0, beta)
- FIFE (C++, Python, LGPL-2.1, beta)
- Fire Madness (Pascal, GPL-3.0, mature, inactive since 2016)
- Fish Fillets - Next Generation (C++, GPL-2.0, mature)
- Fitzquake (C, GPL-2.0, beta, inactive since 2009)
- Flare (C++, Java, Python, GPL-3.0, mature)
- FlightGear (C++, GPL-2.0, mature)
- flixel-gdx (Java, 3-clause BSD, beta, inactive since 2017)
- FLTK Recycling Game! (C++, LGPL-2.1, mature, inactive since 2014)
- FLTrator (C++, GPL-3.0, mature, inactive since 2016)
- Flukz (C++, GPL-2.0, beta, inactive since 2014)
- FooBillard++ (C, GPL-2.0, mature, inactive since 2012)
- FooBillard (C, GPL-2.0, mature, inactive since 2010)
- Foxy Misfortunes (Pascal, GPL-3.0, mature)
- Free Mars (Java, GPL-3.0, mature)
- freeablo (C++, GPL-3.0, beta)
- Freedoom (None, Python, None, beta)
- Freeminer (C++, Lua, GPL-3.0, beta)
- FreeSims (C#, MPL-2.0, beta)
- FreeSpace 2 Source Code Project (C, C++, Unlicense, mature)
- freeVikings (Ruby, GPL-2.0, beta)
- Frets on Fire (Python, GPL-2.0, mature, inactive since 2008)
- FTEQW (C, GPL-2.0, mature)
- FunLabyrinthe (Pascal, GPL-2.0, mature, inactive since 2012)
- Game Editor (C, C++, GPL-3.0, mature, inactive since 2014)
- GameCake (C, C++, Lua, MIT, mature)
- gamekit (C++, C, zlib, mature, inactive since 2015)
- GamePlay (C++, C, Apache-2.0, mature, inactive since 2016)
- Gang Garrison 2 (Game Maker Script, MPL-2.0, mature)
- GBDK (C, Assembly, C++, MIT, mature)
- GCompris (C, Python, GPL-3.0, mature)
- GeonBit.UI (C#, MIT, mature)
- Gideros (C, C++, Lua, ?, mature)
- Gilbert and the doors (C, GPL-3.0, mature, inactive since 2018)
- GL-117 (C++, GPL-2.0, mature, inactive since 2005)
- glParchis (Python, GPL-3.0, mature)
- GLtron (C, ?, beta, inactive since 2017)
- GNU Chess (C++, GPL-3.0, mature, inactive since 2017)
- GNU FreeDink (C, GPL-3.0, mature, inactive since 2012)
- GNU Go (C, GPL-3.0, mature, inactive since 2011)
- Go Ollie! (?, GPL-3.0, mature, inactive since 2011)
- Golly (C++, Java, GPL-2.0, mature)
- GoRogue (C#, MIT, mature)
- Gottet (C++, GPL-3.0, mature)
- Goxel (C, C++, GPL-3.0, beta)
- GPL Arcade Volleyball (C++, GPL-2.0, beta, inactive since 2006)
- Gravitation (C++, Public domain, mature, inactive since 2008)
- Grobots (C++, GPL-2.0, mature, inactive since 2014)
- GUSANOS (C++, GPL-2.0, beta, inactive since 2006)
- Gusty's Serpents (C++, GPL-3.0, beta, inactive since 2014)
- GZDoom (C, C++, GPL-3.0, mature)
- Hammer of Thyrion (C, GPL-2.0, mature)
- Hardwar (C++, GPL-3.0, beta, inactive since 2015)
- Harmonist: Dayoriah Clan Infiltration (Go, ISC, beta)
- HaxePunk (Haxe, MIT, mature)
- Head over Heels (C++, GPL-3.0, mature)
- Heart of the Alien (C, GPL-2.0, beta, inactive since 2005)
- Hedgewars (Lua, C, C++, Pascal, Haskell, GPL-2.0, mature)
- Help Hannah's Horse (C++, GPL-2.0, beta, inactive since 2008)
- Hexoshi (Python, GPL-3.0, beta, inactive since 2016)
- HGE (C, Haskell, zlib, beta, inactive since 2013)
- HoDoKu (Java, GPL-3.0, mature, inactive since 2013)
- Holtz (C++, GPL-2.0, mature)
- HoverRace (C++, Custom, mature, inactive since 2016)
- HyperRogue (C++, GPL-2.0, mature)
- I Have No Tomatoes (C++, zlib, mature, inactive since 2004)
- Ice Breaker (C, GPL-2.0, mature, inactive since 2003)
- iiChantra (C++, MIT, beta, inactive since 2012)
- ika (C++, Python, PHP, C#, GPL-2.0, beta, inactive since 2007)
- Inexor (C++, JavaScript, zlib, beta, inactive since 2018)
- Infinite Mario Bros (Java, 3-clause BSD, mature, inactive since 2010)
- Infinite Tux (Java, GPL-3.0, Public domain, mature)
- Infon Battle Arena (C, Lua, GPL-2.0, beta, inactive since 2012)
- INSTEAD (C, Lua, Java, MIT, mature)
- Intersect (C#, MIT, GPL-2.0, beta)
- Intricacy (Haskell, GPL-3.0, beta)
- ioquake3 (C, GPL-2.0, mature)
- iortcw (C, C++, GPL-3.0, mature)
- irrlamb (C, C++, GPL-3.0, mature)
- Jake2 (Java, GPL-2.0, beta, inactive since 2006)
- Jamp (C++, GPL-3.0, beta, inactive since 2009)
- Javelin (Java, GPL-2.0, mature, inactive since 2016)
- Jazz² Resurrection (C#, JavaScript, GPL-3.0, mature)
- JGame (Java, 3-clause BSD, mature, inactive since 2012)
- JonoF's Shadow Warrior Port (JFSW) (C, GPL-2.0, beta, inactive since 2005)
- JSkat (Java, GPL-3.0, Apache-2.0, beta)
- JSoko (Java, GPL-3.0, mature)
- Julius (C, C++, AGPL-3.0, mature)
- Jump Don't Die (Java, GPL-3.0, mature)
- Jump'n'Bump (C, GPL-2.0, mature, inactive since 2004)
- KeeperRL (C, C++, GPL-2.0, beta)
- KevEdit (C, GPL-2.0, mature)
- Key Runner (C++, Script, GPL-3.0, mature, inactive since 2013)
- kiki the nano bot (C++, Public domain, mature, inactive since 2007)
- Killer Crates (Java, MIT, beta, inactive since 2017)
- KlayGE (C++, GPL-2.0, mature)
- Knights (C++, GPL-3.0, beta, inactive since 2014)
- Kobo Deluxe (C++, GPL-2.0, beta, inactive since 2007)
- Krank (Python, Public domain, beta, inactive since 2008)
- Kryftolike (Pascal, GPL-3.0, mature)
- L'Abbaye des Morts (C, GPL-3.0, mature, inactive since 2018)
- LambdaHack (Haskell, 3-clause BSD, beta)
- LambdaRogue: The Book of Stars (Pascal, GPL-2.0, mature, inactive since 2012)
- LGames (C++, GPL-2.0, mature)
- Liberal Crime Squad (C++, GPL-2.0, mature, inactive since 2012)
- Librelancer (C, C#, MIT, beta)
- LibreMines (C++, GPL-3.0, mature)
- LIKO-12 (Lua, Rust, MIT, mature)
- LimonEngine (C, C++, LGPL-3.0, beta)
- LionEngine (Java, GPL-3.0, mature)
- Loon Game (Java, C#, Apache-2.0, beta)
- Love2dCS (C#, C++, MIT, mature)
- LPairs (C++, GPL-3.0, mature, inactive since 2021)
- Lugaru (C++, GPL-2.0, mature)
- Luola (C, GPL-2.0, mature, inactive since 2005)
- LÖVE (C++, zlib, mature)
- Maelstrom (C, C++, GPL-2.0, mature, inactive since 2002)
- Mafia: Toolkit (C#, MIT, mature)
- MafiaUnity (C#, Apache-2.0, beta, inactive since 2020)
- MAGE - Matthias Advanced Game Engine (C++, GPL-3.0, beta)
- Magical Life (C#, MIT, beta)
- ManaPlus (C++, GPL-3.0, mature)
- ManiaDrive (PHP, ?, mature, inactive since 2008)
- Manic Digger (C#, Public domain, Unlicense, mature, inactive since 2017)
- Marble Marcher (C++, GPL-2.0, mature)
- Mari0 (Lua, MIT, mature, inactive since 2012)
- Maxit (C++, 3-clause BSD, mature, inactive since 2014)
- Mazer (Pascal, GPL-3.0, beta, inactive since 2018)
- Me and My Shadow (C++, GPL-3.0, beta)
- Mega Mario (C++, LGPL-2.1, mature, inactive since 2012)
- MekWars (Java, GPL-2.0, mature)
- Metaforce (C, C++, MIT, beta)
- Metar Sweeper (Pascal, GPL-3.0, beta, inactive since 2015)
- MicroWar 2.0 (Python, 3-clause BSD, mature, inactive since 2009)
- Mindustry (Java, GPL-3.0, mature)
- Minetest (C, C++, Lua, LGPL-2.1, mature)
- mini2Dx (Java, C#, Apache-2.0, mature)
- Minilens (GDScript, GPL-3.0, mature, inactive since 2018)
- Mininim (C, GPL-3.0, beta, inactive since 2017)
- MiniPacman (Ada, GPL-3.0, mature)
- Moagg2 (Java, GPL-2.0, mature, inactive since 2008)
- Mojotron: Robot Wars (C++, GPL-2.0, mature, inactive since 2019)
- Monofoxe (C#, MIT, mature)
- Monsterz (Python, WTFPL, beta, inactive since 2007)
- Moonbase Assault (Java, MIT, beta, inactive since 2019)
- Moubootaur Legends (C, C++, Script, GPL-3.0, beta)
- Mr. Rescue (Lua, zlib, mature, inactive since 2016)
- Murder In The Public Domain (C++, GPL-3.0, mature, inactive since 2013)
- Nazara Engine (C, C++, MIT, beta)
- ncurses (C, MIT, mature)
- neoGFX (C++, GPL-3.0, beta)
- NetMauMau (C++, LGPL-3.0, mature, inactive since 2015)
- NetRadiant-custom (C++, C, GPL-2.0, mature)
- Netrek (C, Custom, mature, inactive since 2009)
- Neverball (C, C++, GPL-2.0, mature)
- Nexuiz (C++, GPL-2.0, mature)
- NFSIISE (C, MIT, mature)
- Nikwi (C++, GPL-2.0, beta, inactive since 2012)
- No Gravity (C, GPL-2.0, mature, inactive since 2006)
- Noiz2sa (C, C++, 2-clause BSD, beta, inactive since 2004)
- Not Pacman (Lua, WTFPL, mature, inactive since 2013)
- NOVA PINBALL (Lua, GPL-3.0, beta, inactive since 2017)
- NStars! (C#, ?, beta, inactive since 2004)
- NullpoMino (Java, 3-clause BSD, mature)
- Numpty Physics (C++, GPL-3.0, beta, inactive since 2016)
- nXtank (Python, C++, GPL-3.0, beta, inactive since 2010)
- OGS Mahjong (C++, GPL-3.0, mature, inactive since 2016)
- OldSkool Gravity Game (C++, C, GPL-3.0, mature, inactive since 2016)
- ONScripter (C++, GPL-2.0, mature, inactive since 2020)
- Oolite (Objective-C, C, JavaScript, GPL-2.0, mature)
- Open Fodder (C, C++, GPL-3.0, mature)
- Open Game Engine (C++, LGPL-2.1, beta, inactive since 2008)
- Open Horizon (C++, MIT, beta)
- Open Kick-Off (Java, MIT, beta)
- Open Quartz (C, GPL-2.0, beta, inactive since 2004)
- Open Rodent's Revenge (C++, MIT, beta, inactive since 2018)
- Open RSC (Java, C++, C, Objective-C, AGPL-3.0, mature)
- Open Yahtzee (C++, GPL-2.0, mature, inactive since 2016)
- OpenAlchemist (C++, GPL-2.0, beta, inactive since 2010)
- OpenArena (C, GPL-2.0, mature, inactive since 2012)
- openblack (C, C++, GPL-3.0, beta)
- OpenBlok (C++, GPL-3.0, beta)
- OpenBlox (Python, Lua, GPL-3.0, beta, inactive since 2011)
- OpenBVE (C#, Public domain, mature)
- OpenClonk (C, C++, ISC, mature)
- OpenDiablo2 (Go, GPL-3.0, mature)
- OpenDungeons (C++, GPL-3.0, beta)
- OpenGothic (C++, MIT, beta)
- OpenHoW (C, C++, GPL-3.0, beta)
- OpenHV (C#, Lua, GPL-3.0, beta)
- OpenJazz (C++, GPL-2.0, beta)
- OpenJK (C, C++, GPL-2.0, beta)
- OpenKrush (C#, GPL-3.0, beta)
- OpenLara (C++, C, 2-clause BSD, mature)
- OpenLieroX (C++, LGPL-2.0, mature)
- OpenLoco (C++, MIT, mature)
- OpenMortal (C++, Perl, GPL-2.0, beta, inactive since 2006)
- openMSX (C++, GPL-2.0, mature)
- OpenOMF (C, C++, MIT, beta)
- OpenRCT2 (C++, GPL-3.0, mature)
- OpenRW (C, C++, GPL-3.0, beta)
- OpenSAGE (C#, LGPL-3.0, beta)
- OpenSolomonsKey (C++, Unlicense, beta)
- OpenSpades (C, C++, AngelScript, GPL-3.0, beta)
- OpenSupaplex (C, GPL-3.0, mature)
- OpenTESArena (C++, MIT, beta)
- OpenTomb (C, C++, Lua, LGPL-3.0, beta)
- OpenTyrian (C, GPL-2.0, beta, inactive since 2018)
- OpenVIII (C#, MIT, beta)
- OPMon (C++, GPL-3.0, beta)
- opsu! (Java, GPL-3.0, mature)
- Oreon Engine (Java, GPL-3.0, mature)
- osu! (C#, MIT, beta)
- ouzel (C, C++, Objective-C, 2-clause BSD, beta)
- Overgod (C, GPL-2.0, mature, inactive since 2005)
- Overload (C, C++, MIT, mature)
- Pacewar (Python, GPL-3.0, mature, inactive since 2017)
- Pachi (C, Python, GPL-2.0, mature)
- PainTown (C++, Java, Python, 3-clause BSD, mature)
- PARSEC47 (D, 2-clause BSD, beta, inactive since 2003)
- Passage (C++, Public domain, mature, inactive since 2011)
- Penguin Command (C, GPL-2.0, mature, inactive since 2007)
- Pentagram (C++, GPL-2.0, beta, inactive since 2018)
- Performous (C, C++, GPL-2.0, mature)
- PGU (Python, LGPL-2.1, mature)
- Physics Platformer (Java, MIT, beta, inactive since 2019)
- Physics Spacewar (Java, MIT, beta, inactive since 2019)
- Pillows (Python, GPL-2.0, beta, inactive since 2007)
- Pingus (C++, Scheme, GPL-3.0, mature)
- Pink Pony (C++, GPL-3.0, mature, inactive since 2017)
- PipeWalker (C++, GPL-3.0, beta, inactive since 2012)
- Pixel Dungeon (Java, GPL-3.0, mature, inactive since 2015)
- Pixel Wheels (Java, GPL-3.0, beta)
- PixelLight (C, C++, MIT, mature, inactive since 2012)
- Planet Rider (GDScript, GPL-3.0, mature, inactive since 2015)
- PLIB (C++, LGPL-2.0, mature, inactive since 2012)
- PokerTH (C++, AGPL-3.0, mature, inactive since 2017)
- Powerslave EX (C, C++, GPL-3.0, beta, inactive since 2017)
- Powerslide remake (C++, MIT, beta)
- Primrose (C++, Public domain, mature, inactive since 2009)
- Privateer - Gemini Gold (C++, GPL-2.0, mature, inactive since 2012)
- Procedural Map Generator (C++, MIT, mature, inactive since 2018)
- Project Helena (Pascal, GPL-3.0, beta, inactive since 2018)
- Project-Uranium-Godot (GDScript, MIT, beta)
- Project: Starfighter (C, GPL-3.0, mature)
- Psyco (C, MIT, mature, inactive since 2008)
- Puzzle Moppet (C++, WTFPL, mature, inactive since 2015)
- PyChess (Python, TypeScript, GPL-3.0, mature)
- Pygame---Alien-Invasion (Python, GPL-3.0, beta, inactive since 2018)
- PyKaraoke (Python, C, LGPL-2.1, beta, inactive since 2011)
- pyscroll (Python, LGPL-3.0, mature, inactive since 2018)
- PySol (Python, GPL-2.0, mature, inactive since 2004)
- PyTMX (Python, LGPL-3.0, mature)
- Q (Python, GPL-3.0, mature, inactive since 2013)
- QuakeSpasm (C, GPL-2.0, mature)
- Rabbit Escape (Java, GPL-2.0, mature)
- Race Into Space (C, C++, GPL-2.0, mature)
- raylib (C, C++, C#, zlib, mature)
- Recursive Runner (C++, GPL-3.0, beta, inactive since 2017)
- Reliquarium (Ada, GPL-2.0, mature)
- remc2 (C, GPL-3.0, mature)
- Ren'Py (C, Python, Ren'Py, LGPL-2.1, mature)
- ReShade (C++, 3-clause BSD, mature)
- ResidualVM (C++, GPL-2.0, beta)
- ReTux (Python, GPL-3.0, mature, inactive since 2018)
- rFXGen (C, zlib, mature)
- Ri-li (C++, GPL-3.0, mature, inactive since 2007)
- Rigs of Rods (C, C++, AngelScript, GPL-3.0, mature)
- Rocks'n'Diamonds (C, GPL-2.0, mature)
- RogueBox Adventures (Python, GPL-3.0, mature)
- Rolisteam (C++, JavaScript, GPL-2.0, mature)
- Rott94 (C, C++, GPL-2.0, beta)
- RPG-X (C, GPL-2.0, mature, inactive since 2015)
- rpgboss (Scala, JavaScript, AGPL-3.0, beta, inactive since 2017)
- rRootage (C, 2-clause BSD, beta, inactive since 2004)
- Ruby-warrior (Ruby, MIT, beta, inactive since 2012)
- RufasCube (Ada, GPL-2.0, mature)
- RufasSlider (C++, GPL-2.0, mature)
- RufasSwap (Ada, GPL-3.0, mature)
- SanAndreasUnity (C#, MIT, mature)
- Sanity Engine (C++, MPL-2.0, beta)
- Scorched3D (C++, GPL-2.0, mature, inactive since 2014)
- Scrabble3D (Pascal, GPL-3.0, mature, inactive since 2015)
- Scrolling Game Development Kit 2 (C#, GPL-2.0, mature, inactive since 2017)
- Settlers III remake (Java, MIT, beta)
- Seven Kingdoms: Ancient Adversaries (C++, GPL-2.0, mature)
- sfxr (C++, MIT, mature, inactive since 2012)
- Shattered Pixel Dungeon (Java, GPL-3.0, mature)
- Shockolate (C, GPL-3.0, beta)
- Shotgun Debugger (C++, GPL-2.0, mature, inactive since 2005)
- Simon Tatham's Portable Puzzle Collection (C, MIT, mature)
- Simple Platformer (Java, MIT, beta, inactive since 2019)
- Simsu (C++, GPL-3.0, mature)
- SLADE (C++, GPL-2.0, mature)
- Slick2D (Java, 3-clause BSD, beta, inactive since 2014)
- Slime Volley (C, GPL-3.0, mature, inactive since 2010)
- Slingshot (Python, GPL-2.0, beta, inactive since 2007)
- Sludge (C, C++, Objective-C, LGPL-2.1, mature)
- Smash Battle (C++, GPL-2.0, beta, inactive since 2011)
- Snelps (Ruby, LGPL-2.1, beta, inactive since 2012)
- SoftPixel Engine (C++, C, zlib, mature, inactive since 2013)
- SokoSolve (C#, GPL-3.0, mature, inactive since 2009)
- SolarWolf (Python, LGPL-2.1, mature, inactive since 2004)
- Soldat (C, Pascal, MIT, mature)
- Sole Collector (Java, MIT, beta, inactive since 2018)
- Sonic Robo Blast 2 (C, C++, GPL-2.0, mature)
- Space Harrier Clone (C, C++, MIT, beta, inactive since 2018)
- SpaceCadetPinball (C++, MIT, mature)
- SpacePeng! (Java, GPL-3.0, mature, inactive since 2017)
- SpaceTrader for Java (Java, GPL-2.0, mature, inactive since 2010)
- Spartan Engine (C, C++, MIT, beta)
- Spice Trade (Java, LGPL-2.1, mature, inactive since 2005)
- StarBlastrix (C++, GPL-2.0, beta, inactive since 2006)
- Stareater (C#, GPL-3.0, beta)
- StepMania (C, C++, Lua, MIT, mature)
- SteveTech1 (Java, MIT, beta, inactive since 2019)
- Stockfish (C++, GPL-3.0, mature)
- Storm Engine (C++, GPL-3.0, mature)
- Stratagus (C++, GPL-2.0, mature)
- Stunt Rally (C, C++, GPL-3.0, mature)
- Sudokuki (C, Java, GPL-3.0, mature, inactive since 2016)
- Super Bombinhas (Ruby, GPL-3.0, mature)
- Super Methane Brothers (C++, GPL-2.0, mature, inactive since 2011)
- SuperStarfighter (GDScript, MIT, beta)
- SuperTux (C++, GPL-3.0, beta)
- SuperTuxKart (C++, C, GPL-3.0, mature)
- SuperTuxParty (GDScript, GPL-3.0, beta)
- Swappy Jigsaw (Pascal, GPL-3.0, mature, inactive since 2019)
- System Syzygy (Rust, GPL-3.0, mature, inactive since 2018)
- T^3 (C++, GPL-2.0, beta, inactive since 2005)
- Tactics Squad (C++, GPL-2.0, beta, inactive since 2007)
- Taisei Project (C, Python, MIT, mature)
- Tangomon (Python, GPL-3.0, mature, inactive since 2017)
- TankistOnline (Python, GPL-3.0, beta)
- Tanks of Freedom (GDScript, MIT, mature)
- Team Tactics (Java, MIT, beta, inactive since 2016)
- Teeworlds (C, C++, zlib, beta)
- TermFrogger (Ada, GPL-3.0, mature)
- TerminalApps (Ada, GPL-3.0, mature)
- TES3MP (C++, GPL-3.0, beta)
- Tetrepetete (C++, GPL-2.0, mature)
- The Battle for Wesnoth (C, C++, Java, Python, Lua, GPL-2.0, mature)
- The Bub's Brothers (Python, C, MIT, mature, inactive since 2013)
- The Butterfly Effect (C++, GPL-2.0, beta)
- The Dark Mod (C++, GPL-3.0, mature)
- The Endless Dungeons (C, CC-BY-NC-SA-2.0, mature, inactive since 2015)
- The Eternity Engine (C, C++, GPL-3.0, mature)
- The Legend of Edgar (C, GPL-2.0, mature)
- The Mana World (C++, Script, GPL-2.0, mature)
- The Powder Toy (C++, C, Lua, Python, GPL-3.0, mature)
- The Secret Chronicles of Dr. M. (C++, GPL-3.0, mature)
- Thrive (C++, AngelScript, JavaScript, C#, GPL-3.0, beta)
- Thrust (C, GPL-2.0, beta, inactive since 2006)
- TIC-80 (C, Java, C++, Lua, MIT, beta)
- TinTin++ (C, GPL-3.0, mature)
- Toppler (C++, GPL-2.0, mature, inactive since 2012)
- TORCS, The Open Racing Car Simulator (C++, C, PHP, GPL-2.0, mature, inactive since 2016)
- Torque 2D (C++, C, MIT, mature)
- Torque 3D (C++, C, MIT, mature)
- Total Annihilation 3D (C++, C, Lua, GPL-2.0, beta, inactive since 2017)
- Transcend (C++, ?, beta, inactive since 2005)
- Tremulous (C, GPL-2.0, mature, inactive since 2016)
- Tressette (C++, GPL-2.0, mature, inactive since 2017)
- Trigger (C++, GPL-2.0, beta)
- Trip on the Funny Boat (Python, GPL-2.0, mature, inactive since 2007)
- TROPHY (C++, GPL-2.0, mature, inactive since 2012)
- TTDPatch (Assembly, C, C++, GPL-2.0, mature, inactive since 2013)
- Tumbly Towers (Java, MIT, beta, inactive since 2017)
- Tumiki Fighters (D, C++, 2-clause BSD, mature, inactive since 2005)
- TUSSLE (Python, GPL-3.0, mature, inactive since 2017)
- Tux Builder (GDScript, GPL-3.0, beta)
- Tux Football (C++, GPL-2.0, beta, inactive since 2012)
- Tux Paint (C, C++, GPL-2.0, beta)
- Tuxemon (Python, GPL-3.0, beta)
- UAlbion (C#, MIT, beta)
- Uebergame (TorqueScript, C#, MIT, mature)
- Ultimate Stunts (C++, GPL-2.0, beta, inactive since 2013)
- UltraStar Deluxe (Pascal, GPL-2.0, mature)
- UltraStar Play (C#, MIT, beta)
- Umoria (C, C++, GPL-3.0, mature)
- UnCiv (Kotlin, MPL-2.0, beta)
- unitystation (C#, AGPL-3.0, beta)
- Unvanquished (C, C++, GPL-3.0, mature)
- Vanilla-Conquer (C, C++, Assembly, GPL-3.0, mature)
- VASSAL (Java, LGPL-2.1, mature)
- VCMI (C++, GPL-2.0, mature)
- VDrift (C++, GPL-3.0, mature, inactive since 2014)
- Vectoroids (C, GPL-2.0, mature, inactive since 2002)
- Veraball (GDScript, MIT, beta, inactive since 2016)
- Violetland (C++, GPL-3.0, beta)
- Visual Pinball (C++, MAME, mature)
- vitetris (C, 2-clause BSD, beta)
- vkQuake (C, C++, GPL-2.0, mature)
- Vocaluxe (C#, C++, GPL-3.0, beta, inactive since 2018)
- Vorton (C, GPL-3.0, beta, inactive since 2004)
- Voxelands (C++, C, GPL-3.0, beta)
- VQEngine (C++, GPL-3.0, beta)
- Wagic, the Homebrew (C++, C, Objective-C, 3-clause BSD, beta)
- warcraft-remake (Java, GPL-2.0, beta)
- Which Way Is Up? (Python, GPL-2.0, beta, inactive since 2008)
- Wizardry Legacy (C++, C, Objective-C, GPL-3.0, beta, inactive since 2018)
- World Builder (Visual Basic, GPL-2.0, mature, inactive since 2007)
- X-Moto (C++, GPL-2.0, mature, inactive since 2014)
- XBlast (C, Java, GPL-2.0, mature, inactive since 2005)
- Xenowar (C, C++, GPL-3.0, mature, inactive since 2014)
- XPilot NG (C, GPL-2.0, mature, inactive since 2010)
- XPilot (C, C++, GPL-2.0, mature, inactive since 2010)
- XSkat (Java, Custom, mature)
- Yamagi Quake II (C, GPL-2.0, mature)
- Yet Another Engine (MoonScript, Java, Lua, MIT, beta, inactive since 2016)
- Yo Frankie! (Blender Script, ?, mature, inactive since 2009)
- YSoccer (Java, GPL-2.0, mature)
- Zandronum (C, Custom, mature, inactive since 2017)
- Zatacka (C, C++, GPL-2.0, beta, inactive since 2007)
- Zaz (C++, GPL-3.0, beta, inactive since 2010)
- ZDoom (C, C++, ZenScript, GPL-3.0, mature)
- Zelda Classic (C, C++, GPL-3.0, mature)
- Zero Ballistics (C++, MIT, mature, inactive since 2013)
- ZGB (C, Assembly, C++, MIT, mature)
- Zod Engine (C++, ?, mature, inactive since 2018)