So, could this be used to compile an OS, so it would mostly run on the GPU, and also say, python itself, perhaps V8, an an x86 emulator, stuff like that?
Yes that is the ultimate goal! Although that is obviously a far future. Currently we only have funding to provide a few toy languages, but hopefully the results will be good enough to draw attention so we can scale and broaden support to more and more languages!
Someone did run Linux in a pixel shader on VRChat.