Even worse, if you've ever accepted a patch or pull request and didn't get copyright transferred to you, then that code is still owned by the author of the patch, and you'll need their permission too.

edit: I don't think forked repos are much of a problem. They're already on Github, so they already accepted the ToS. if they didn't, that's not your problem as a forkee. Unless the code was forked before this new ToS. Copyright is so messy.