Looks like 10GB in the README[0] for a 512x512 image - though the fork[1] from the repo in this PR claims to be able to work with as little as 4GB VRAM.
Yeah, every time a typeface is shared on here it is met with some opposition since most cost money for individuals/personal use. I understand it's hard to take the time to design a nice typeface and that the creators should be compensated for their work, but sadly it means fonts like these are practically limited to commercial use. I wonder if there's a better way to turn a profit on typefaces - there's been a handful of really interesting ones posted on HN I've wanted to try.
[0] https://github.com/CompVis/stable-diffusion#stable-diffusion [1] https://github.com/basujindal/stable-diffusion#txt2img