Mainly because it might be more in line with traditional FOSS ideals to take our marbles and go home? It's hardly a temper tantrum. After the Linux kernel got into one too many arguments with Bitkeeper, there was an inflection point where Torvalds got fed up and just wrote git instead. I think this is an inflection point like that. And "taking Github to court" is much easier said than done for a FOSS project, although I assume that someone will be doing that at some point.
> So, we have to move all that, to another host: who is to say that other host will always be a better FOSS steward? who is to say that other host has anyone near the level of features? An integrated CI/CD and hosting of release artifacts is huge.
In addition to GitLab, I think Sourcehut offers similar features and is also FOSS (AGPLv3).
> So, on the premise that our license has been violated, instead of sue'ing, we should take our FOSS somewhere else? Again, the list is large, we need to migrate all of that.
I don't think anyone is telling you what to do, just offering suggestions. My suggestion is that switching to a forge that respects FOSS is a reasonable alternative to legal action against GitHub or just ignoring the potential license violations via Copilot. You can of course choose any of the alternatives, or the status quo; which is what you seem to have largely convinced yourself is fine. Good luck, and thanks for working on FOSS anyway!