I think you heard wrong. My understanding is Radeon drivers are open source, and nVidia drivers are closed.
This is why Linus said, "F*ck, nVidia."
You are correct about the quote, but ATI's open source drivers don't perform as well as their proprietary drivers, and Nvidia's proprietary perform much better than ATI's. I'm not sure if this is something that will change in the longterm, because I usually do prefer ATI products