Is this standalone, as in: an actual file format people can use? From their website it looks like it won't work without using their service or hosting something yourself?
Looks like you can compile files as shown here: https://github.com/typst/typst?tab=readme-ov-file#usage
Yes, there is a standalone compiler for typst that you can use offline for free. Source code is here https://github.com/typst/typst/