The complication is that most CUDA apps you would want to run on ZLUDA contain first-party libraries provided by Nvidia (e.g. cuDNN) which may have restrictive

The complication is that most CUDA apps you would want to run on ZLUDA contain first-party libraries provided by Nvidia (e.g. cuDNN) which may have restrictive license terms saying you're not allowed to run them on a third-party runtime. ZLUDA itself may be legally in the clear as a cleanroom reimplementation free of Nvidia code, but it's not so clear-cut for the users of ZLUDA.