IMO there's one primary reason Nvidia does not release open source drivers, and never will, despite whatever they say now.
It has nothing to do with lawyers, or protecting hardware secrets - that's all just smokescreen to obscure the real reason.<p>If open source drivers were available, it would be possible to port the low level code to any operating system environment anyone wanted to. And that means <i>future</i>, <i>experimental</i> operating systems and GUIs too.
Effectively this would enable OS/GUI innovation, allowing radical new 3D graphics based UIs, escaping the Microsoft Windows, Linux and Apple trap.<p>Considering the dismal state of UIs now (Windows 8, cough, say no more) you can imagine what the appearance of a well designed, sensible and user-enabling OS/GUI in the next few years would do to Microsoft.<p>Open source 3D drivers would definitely result in a quite rapid overturn of the present OS monopoly-by-three applecart. So the powers that be in the personal computer market are going to allow it ... over their dead bodies.<p>Incidentally, 3Dfx did make the full source code for their Glide drivers available (for money.) I worked at a company that bought the 3Dfx drivers, and I personally ported the drivers (which were Windows & Linux targeted) to a minimal MIPS processor based platform intended for gambling machines. It worked - passed all the test code. Then the company went through a 'local CEO was ripping off the company, sack him and kill all his projects' spasm, and the machine never got to market. Soon after that 3Dfx was deep sixed and their patents sucked into the Nvidia pool.<p>Personally I've always suspected those events may have had something to do with certain parties making sure an open source 3D engine never happened - precisely because it would be a threat to the OS status quo.