That's a good point, although I'd argue that anything is less proprietary than something that literally runs only on a single vendor's hardware.

Also, I feel that proprietary shouldn't be used as a synonym to targeted at specific hardware, because being truly independent of the hardware might just be too much to ask for.

But it's interesting to consider why HIP doesn't support compiling to OpenCL. They don't seem to address this in the FAQs, but I think the reason might be that in addition to all the other problems, OpenCL is terrible as an intermediate language for compiling C++ to OpenCL. If it wasn't, then I don't know a good reason for why something like HIP wouldn't support it out of the box. I mean, compiling C++ to C basically requires a full-blown C++ compiler, which is a huge investment of resources, so I really wonder how the decision was made to base OpenCL on C99. Because of all this, I'm not sure how to understand HIP in relation to the rest of the ecosystem.