[simonh]

GPUs are hardware, not software. The patent situation there is much clearer. Critical hardware features of GPUs belong to different companies and the licenses for using those features often include highly restrictive licences for the code that drives them, or contractual obligations to use and not publish such code because doing so would reveal internal details of the hardware implementation of those features, which are trade secrets. Many drivers also load proprietary microcode into the CPU. AMD's 'Open Source' drivers do this.

Put simply, the GPU vendors do not actually own all the rights to their own driver software. AMD had a project to improve the state of their drivers on Linux, but the approach they took was to try and rewrite and open source the code implementing the public API to the closed binary blobs inside the drivers, to make it easier to maintain the stability of the drivers across kernel versions. Open sourcing the blobs wasn't possible for AMD because the code in them just doesn't belong to AMD.

>Don't just accept it when lawyers say no.

Which lawyers though? It's not necessarily ARM lawyers that are the problem. You'd need to get agreement from the dozens of patent holders of various bits of the technology, most of whom are unknown as their identities are confidential.