Initiatives like this make me really excited, but the biggest problem is always long term maintainability and interoperability with the rest of the browser ecosystem. Without a huge company backing the effort, it becomes really risky to use this long term because development could drop off or never gain traction.

If you don't have a huge open source community, you need one to push the ball forward and keep things going. That's really hard to get without users, which is a great catch 22. I'd almost suggest building a "killer web app" on Fengari just to demonstrate it, or at least to indicate that its development effort won't go the way of Moonshine.

I love Lua, and I would love to use this. The risk, however, is pretty high in anything but an experimental context -- at least for me.