I hope this gets mirrored somewhere else, because I don't trust GitHub to not cave in to legal demands despite RE being legal regardless of EULA in parts of the world, and the extra attention this gets may otherwise kill it.
Not saying you shouldn't fork or fear, but GitHub and Google are generally good actors compared to others.
Going after GitHub means that GitHub has to shut down and the opponent sticks with their legal costs.
When attacking Microsoft they have enough cash to pay you out (in case they lose or they accept a payment to make you shut up) and the case might disrupt Microsoft enough to give you an advantage in a different field.
Not saying that Google would sue Microsoft. Would be very bad for their image. But a risk evaluation is different.
And if they do that, nobody will have a copy of this source code?
Wouldn't be the first time, either: https://www.zdnet.com/article/google-shuts-down-gaia-efforts...
TL;DR: They shut down an open source GEarth clone called Gaia a decade ago, although they managed to not to lose a lot of karma over that due to graceful handling.
I do that for anything that looks predictably hot