The source code is under a FLOSS license, but it only works on Nvidia GPUs and uses proprietary Nvidia-specific technologies like CUDA.
It's significantly closer to "nonfree" on the free-nonfree spectrum than it should be, and is another example of the difference between the guiding philosophies behind "free software" and "open source"
Can't you run it on CPU? And looking at the code, it seems like they're using Numba to JIT their CUDA kernels, so I guess someone could come along and provide a compatibility shim to make the kernels run on a non-CUDA accelerator?
It's significantly closer to "nonfree" on the free-nonfree spectrum than it should be, and is another example of the difference between the guiding philosophies behind "free software" and "open source"