They opened a tiny kernel level sliver of their driver, everything else (including OpenGL stack et al) is and will still be closed.

Sadly, a couple of years ago someone seriously misunderstood the news about "open sourcing" their drivers and spread that misunderstanding widely; many people now think their whole driver stack is open, when in reality it's like 1% of the code — the barest minimum they could get away with (I'm excluding GSP code here).

The real FOSS driver is Nova, and it's driven by the community with zero help from Nvidia, as always.