I agree that the exact licensing terms are somewhat relevant if you intend to depend on this software.
However, it's worth noting that the compiler in question is LLVM based. So you can construct your own compiler frontend that generates LLVM IR code that can be compiled for CUDA by their backend. It's very likely that there are some CUDA-specific LLVM intrinsics, so the frontend will not be entirely independent of CUDA compiler licensing terms but at least now you have a somewhat open interchange format to use between your frontend and the CUDA backend.
However, it's worth noting that the compiler in question is LLVM based. So you can construct your own compiler frontend that generates LLVM IR code that can be compiled for CUDA by their backend. It's very likely that there are some CUDA-specific LLVM intrinsics, so the frontend will not be entirely independent of CUDA compiler licensing terms but at least now you have a somewhat open interchange format to use between your frontend and the CUDA backend.