Develop game using nvidia toolsets = some middlewares run on non-NVIDIA hardware, but those usually doesn't run well, you want to optimize them but you cannot by license agreements. Other simply do not run at all on non-NVIDIA hardware and you cannot rewrite the implementation to run on other hardware by license agreement. Develop game using AMD (Intel) toolsets = all middlewares run on non-AMD (non-Intel) hardware, but those usually doesn't run well, you are free to optimize for other architecture. Yes I also included Intel because the situation it's more or less the same as AMD. This is a huge difference. If some part of the code is optimized with NVAPI or AGS is not an issue, license agreements and the lack on the NVIDIA side of some part of the source code are the only issue. I could also add the fact you cannot use the complete version of NVAPI without a closed agreement, but that's not the point.... I can guess you never wrote a single line of code that is hardware dependent on performance side: no-one mentally sane would just make a past and copy of those middlewares, nor it could work. Coding games, which involves system programming too, is not like playing with Lego, regardless some inpet people want make you believe that.