I think there's two issues at play: re-implementing the CUDA APIs, and using that re-implementation to run Nvidias own libraries like cuDNN on non-Nvidia hardwa

I think there's two issues at play: re-implementing the CUDA APIs, and using that re-implementation to run Nvidias own libraries like cuDNN on non-Nvidia hardware. Precedent around emulation and the Google vs. Oracle case probably protects the former, but Nvidia is probably entitled to say how you're allowed to use their own software in the latter.