The largest wasm file I see downloaded on the website is 440K. Disassembling it, it seems to contain a bunch of libc-like filesystem code, and was built using the rust toolchain. So it doesn't look like v8 has been compiled to wasm here.

Rather, I assume they compiled a library or two, but otherwise they use the JS VM in the browser, and they've ported the Node.js runtime scripts to that environment.

That doesn't take anything away from the achievement here - it's really impressive! It's better to use the VM in the browser, if you can get those runtime scripts portable enough, which from other comments it seems like the answer is (or will be) yes.