Working on it. Libev-based. It's a spare-time project of mine. I have the "portable but not particularly scalable" pure Lua and luasocket backend done (for easy development + light deployment on Windows), working on the error handling in the libev backend now.

Much of the complexity comes from error handling, not just the async IO. Erlang gets that right, too. I don't know how much error handling node.js does. (I plan on checking it out eventually, since my framework will be compared to it.)

I don't have a time frame yet. I'm also working on a compiler and a bunch of other stuff, and I'm really not a web developer, so it's been a fairly low priority.