In no particular order (yet) here are some answers to some frequently asked on Twitter, Discord, and this forum. Please let me know if anything's unclear or you have more questions and I'll keep this updated :)
> Can we use Unity or Unreal Engine?
> Can we use pre-made assets?
Absolutely, although many people will create their own. I'd recommend adding some attribution in your GitHub repository's README.
> Can we use pre-made code?
The use of game engines, libraries, templates for new games, etc. is fine. In fact, it's highly encouraged! Taking a game you've been working on for months, or forking a game and changing some pixels is probably not in the spirit of the jam :)
> Can we sell the games (for the jam or post jam)?
> Is there a twitter hashtag?
The official hashtag is #GitHubGameOff. We love 💙❤️ seeing work-in-progress screenshots throughout the month! <3
> Are games allowed if they contain 18+ content?
No restrictions on content, but if it's something I wouldn't show my kids or grandparents... then it may be less likely that it'll appear on our blog :) Please also see itch.io's note on adult content.
> What are the voting categories?
Similar to last year, games will be rated on the following: Overall, Gameplay, Graphics, Audio, Innovation and Theme Interpretation.
> What kinds of licenses are required/accepted for the public GitHub repo?
You're welcome to use whatever kind of license you wish! See this documentation for tips on choosing / applying a license.
> Can I edit the game after the submission period?
Please don't change the game on the itch.io page until after the voting period ends. If there's a bug that seriously affects/prevents playability that's a "quick fix", please feel free to address it. Just leave a note on the itch.io page saying what you changed and why. Since the code is not being judged, you can update the GitHub repository any time.