Questions

Help! I can't run this on my Mac.

On macOS you're likely to receive a warning about how macOS doesn't trust the executable and won't run it, instead giving you the option to move the file to trash, or cancel.

After you see that, you would be able to go into System Preferences, Privacy & Security. Scroll down and you should see an option to run anyway. The next time you run mastodon-bookmark-sync, you'll be prompted again, but after that you should be able to schedule it without worrying.