Licence is MIT / Apache, of course.
EDIT: of course the relicensing is the problem here. Alas we’re in an all-time low interest in Free and Open Source politics, ideologies, and organization so the Big Evil Corpos continue to do their thing, one cog per time.
This was my understanding, but I really am not in the loop enough to say it with certainty, so appreciate the confirmation. I agree, I think we’re seeing from contributions made by people like Valve that there’s real value in requiring derivative work to give back to the community it drew from. But again, I’m really not super well informed. I just tend to pick GNU options when available.