To elaborate further:
- The deal won't be closed for many months (they expect december)
- Microsoft probably won't change github at first (xcept maybe make the login integrate with a Microsoft Account)
- We don't know what they plan to do with the platform in the long term, so worrying now is pointless.
- We don't know that it will EVER be hostile toward ReactOS, even if they break the platform and make it unusable, so chances are we are good.
- If worst comes to worst, as Thomas said, we just say goodbye to GH and move elsewhere.