from disclaimers import IANAL

I'm not sure, but it could be something to do with: http://libv.livejournal.com/26972.html.

Basically, proprietary PowerVR graphics chip driver source was leaked. Anyone who has read the leaked code is considered "tainted" and is unable to contribute to the open-soruce, cleanroom implementation alternative PowerVR drivers.

It generally makes it difficult for ANYONE to develop open-source PowerVR drivers, as their lawyers could argue that they had seen the leaked source code and copied it (regardless of whether or not that fact is true).

The PowerVR chips on Intel platforms came in binary blobs, and were only supported in a few fairly specific configurations. As such, they were obsolete almost as soon as they were released, with little to no support. Thankfully, though, they only put PowerVR chips in their Atom boards for a fairly short period of time, so you won't have to worry about them in these machines.

Intel does a good job producing and supporting their open source graphics drivers. The PowerVR chips aren't designed by Intel, so they don't receive the same level of support.