Excuse the ignorance....
So, is this a 2D nVidia driver, 3D, nForce chipset stuff or ?
It's a 2D driver for most of the NVIDIA chipsets produced so far. It's successfully been tested with TNT2, Geforce2/3/4 and nForce, but as said it should work with most NVIDIA chipsets.
I thought nVidia were a bit closed off to alternate OS driver development.
There are a couple of open source drivers for NVIDIA cards, one comes from XFree86, the other comes from OBOS, both are licensed under a MIT (BSD-like) license. The AROS driver is partly based on the XFree86 one, but it also contains some original stuff not found in any of the other drivers already available.