The OSS Radeon driver is more than sufficient nowadays for non-3d composting of windows and playback of video.
Intels integrated gpu driver is also really good, to the point where you can play ~5 year old games on it just fine with a high end chip.
I wonder how you would pull off OSS hard drive / ram / mobo / psu / etc. It would require that the design schematics and documentation are public. I assume many of them are, but some might not be, and it would be a pain to investigate open hardware.
