It's obvious that the author wants to make a statement, and has their own reason to not expose their work on GitHub. Setting up a mirror would probably contradict these reasons.
If Facebook had bought github, they would have made automated squatting mirrors for all the packages like xscreensaver.
> It's obvious that the author wants to make a statement
Microsoft destroyed his company via illegal means.
Microsoft own GitHub.
https://en.wikipedia.org/wiki/United_States_v._Microsoft_Cor....
https://en.wikipedia.org/wiki/Browser_wars