Well, this is a turn-up for the books: a Kickstarter for "Open Source Graphics Processor (GPU)". !!!
There's a lot of "if's" involved, but it's certainly a very interesting idea, and worth exploring for multiple reasons, education and fun among others.
OSHW and FPGA enthusiasts having their own GPU would be fascinating! 
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PS. I've been wondering whether the Parallella board wouldn't be a nice implementation platform for the programmable pipeline of a modern open-source GPU. After all, the Epiphany device provides hardware parallelism with fast floating point for the core compute engines of 16 to 64 shaders without having to implement CPUs in Verilog. The FPGA would then be left to do only the fastest parts of the overall task instead of implementing the programmable shaders that CPUs are best at.
