At one of the internal Q&As, there was a question as to why we didn't just implement CUDA. One of the reasons given was that the lawyers looked at the license of CUDA and decided that Intel could not legally implement CUDA for Intel's GPU devices. I don't know the details, but quite frankly, it wouldn't surprise me if Nvidia didn't somehow put a poison pill in there to prevent Intel or AMD from implementing it for their own GPUs (note that AMD also doesn't provide an implementation of CUDA for its own GPUs).
Instead, the strategy Intel pursued was to develop a migration tool from CUDA to Sycl: https://software.intel.com/content/www/us/en/develop/tools/o...