Weird project. Apple today released GPTK 2.0 to support ray tracing and AVX1. So they are committed to making it easier and easier to translate Dx11/12 to Metal. Their hardware has fast lanes on the actual silicon to make it even more performant. Vulkan pales in comparison (or rather the DXVK) and caps at Dx11. It can fill in gaps here and there for games that for whatever reason don't work with GPTK but Apple's toolkit is clearly the future.
Not sure why someone would spin this up or waste their time. Am I missing something?