Redstone is a custom Minecraft server written in CoffeeScript. The asynchronous I/O model of Node.js lends itself well to a game server, since most of what's going on is I/O.
We're really excited about this, and while it's far from finished, we want to show it off to our close friends (read: hacker news).
We have two objectives:
Scale to hold hundreds of thousands of players at a time.
Make an elegant server-side modding API.
You can connect to our prototype Creative server at redstone.io and start building penises out of dirt right now. You'll notice a message in your chat sometimes letting you know that you've been handed off to another server. You'll probably also notice some bugs.
We're working on a Minecraft MMO, and we're pumped. Imagine faction warfare on a scale that wasn't possible in Minecraft before now. We're also applying for YC S13.
If you're interested in our MMO, be sure to leave your email below and we'll keep you posted.