[ffn]

If you really don't want to fork someone else's existing repo, want to participate, but can't violate rules, you could always start a project on your account, do a ton of work on it, then start an organization, and have that organization fork your own repo. But honestly, I'm pretty sure github cares more that you wind up with an interesting and fun game at the end of the day rather than you following to the letter about what to fork and not fork.