IANAL, but apart from a private entity having such power being problematic (to say the least) who's going to put stuff on GitHub if it can be gamed to take away your control?
Edit: GH could also be in for liability claims should the original owner re-appear (at least in general, if not this particular case), and would need to check identity of the involved parties and whatnot, which is going to be very costly.
Edit: GH could also be in for liability claims should the original owner re-appear (at least in general, if not this particular case), and would need to check identity of the involved parties and whatnot, which is going to be very costly.