I don't mean to derail discussion about a cool project, but it still seems to imply xterm.js is somehow "improper" emulation (though I might be misreading it).
Terminal emulators are all approximations of terminals, regardless of the programming language.
github: https://github.com/chjj
x: https://x.com/_chjj
keybase: https://keybase.io/chjj
[ my public key: https://keybase.io/chjj; my proof: https://keybase.io/chjj/sigs/WX2-zE10N2fWbWUNf_8PDXWgifPpJWb0PEIs_5oQnbk ]