Have you thought about a pure Javascript implementation of the parser, or compiling the runtime to WASM? Since a parser shouldn't really use any platform features it should be possible - and it could enable using the technology in pure browser based editors (like Monaco, CodeMirror, etc).
Yes! I'm very interested in making the Tree-sitter runtime and all of the parsers available as pre-built WASM modules. I think it should be straightforward to do.
How closely coupled is treesitter to Atom? How difficult would it be to generate binding to treesitter for languages other than Javascript? I dream of a future where elisp bindings for treesitter power syntax highlighting in Emacs.