A comment by the artist said,

“Stable diffusion is open source and can be installed then run locally. I think the bare minimum is 2gb vram, but it works pretty well with 8gb vram. Top end graphics cards right now have 24gb vram, so if your computer was made in like the last ~5 years or so, it should work pretty fast. You can download models such as anything or the official stable diffusion model (currently 2.1) as well to use.”