I did a double take because the title is almost clickbait for us desktop Linux users, and immediately wondered "what's the catch?". It's a significant catch, but also a significant step in the right direction.
It sounds like this "GSP" lets them binary blob their "secret sauce" on the controller itself, so the rest of the driver can be open source now.
Probably all their "enterprise" feature lockouts(vgpu etc..) are in the gigantic firmware that's loaded into GSP. But things that matter to desktop users probably aren't going to be locked out this way.