This is a separate thing with the same name. Although both share some common ideas. The grimfang4/sdl-gpu is a separate library used with SDL, while the new SDL GPU API is directly part of SDL. grimfang4/sdl-gpu is much older and works with today's SDL 2.

The grimfang4/sdl-gpu was one good way to take advantage of modern GPUs in a simple way and workaround the holes/limitations of the old SDL 2D API. The new SDL 3 GPU API will likely make the need for things like grimfang4/sdl-gpu redundant.