To pour some water on the coals: for the _very little_ I know about MBX, so don't take this as absolute truth, there are issues in the way the driver would be structured. While the SGX allows for a mostly userspace based driver, which would simplify IPR and licensing issues, the MBX would need to have all the beef in kernelspace. So that's one more reason why there is little to no interest from Nokia side about it. We are not really so fond of tainting the kernels we ship. About rewiting, there is a small problem: those who would do it have to sign ndas lasting decades.

Anyway, having seen a few demos running on the MBX, let me tell you that they are not too impressive: what i saw was running on a qvga screen and still it wasn't particularly fast. I doubt one would get much performance on a tablet screen withouth having to use pixel doubling and similar tricks.