It’s quite nice to see a fairly complete implementation of Lua for the web. Lua is a much simpler and more approachable language than modern JavaScript, so it’s great to see a strong pathway for using that in the browser. 
@akkartik, is there any chance it provides a pathway for your LÖVE-based programs to appear on the web as well? I guess there are efforts like love.js already, but they seem to use Emscripten, so perhaps Fengari offers a nicer route (depending on whether it assists with graphics APIs). Browsers make some things more difficult though, especially saving state as recently discussed with TiddlyWiki, so perhaps you’re not that interested in deploying to the web.