DMA-BUF is a recent kernel feature that allows multiple GPUs to quickly copy data into each others' framebuffers. A use case would be the NVIDIA Optimus that pairs a fast GPU with an Intel integrated GPU, where the NVIDIA GPU writes into the Intel framebuffer when it is active. But, NVIDIA won't be able to use this infrastructure because it's GPL. Alan Cox replied on LKML to a request from one of their engineers to mark the API non-GPL: "NAK. This needs at the very least the approval of all rights holders for
the files concerned and all code exposed by this change. Also I'd note if you are trying to do this for the purpose of combining
it with proprietary code then you are still in my view as a (and the view
of many other) rights holder to the kernel likely to be in breach
of the GPL requirements for a derivative work. You may consider that
formal notification of my viewpoint. Your corporate legal team can
explain to you why the fact you are now aware of my view is important to
The rest of the thread is worth a read (a guy from RedHat agrees that this code is GPL and cannot become non-GPL without relicensing from a major subset of graphics system contributors). This has a ripple effect: it means that all of the ARM SoC GPU drivers can't use it either, and it may prevent any proprietary drivers for the proposed DRI version 3.
Read more of this story at Slashdot.