"Neither it, its source code, nor its byte code may be modified and recompiled for public use by anyone except us"

This part actually prohibits public forks via the fork button, which for non-paying github users makes it a bit more difficult to contribute :). Might consider adding an exception? :)

This means that while you CAN create forks and submit pull requests, you can't recompile and distribute your changes to the public.

Redistribution constitutes compiling the mod and uploading it for the public to use. It can sit in your forked repository for eternity, but if you want to release it, submit a pull request.

The second line, that i quoted there, is only about source code. If i fork your repository (and i have), and its public (which it is, since i don't pay for github, and thus can't make it private), the source is released to the public per default :). Will come up in a google.

Probably not an issue? :)

^ should make it clearer now.

"However, modified code that has not been merged into the publically available build cannot be redistributed to the public in any form with no exceptions."

From the LICENSE file :)