I don't follow - what does Github and its ownership have to do with anything? I could be wrong, but I was under the impression Linus mirrors on Github just for convience's sake.

I do know that Linus's Github repo is not the official public repository for the kernel -- that's kernel.org's job. And FWIW, relations between the Linux and MS kernel devs have (to my understanding) never been better, especially since the Spectre/Meltdown reveals.