The Spidermonkey/Node.js project has been known for a while now.
Update: I missed a lot of this, but you can find Eich's presentation and notes here Various parts of CoffeeScript may or may not be going into Harmoney. You can find out more about this at in Eich's JSConf talk.
Q: Where will Spidermonkey beat V8 for Node?
A: Spidermonkey is not really in competiton with V8 for Node, but it depends on the workload.
Q: Ryan Dahl asked about debugging.
A: They're working on debuggers.
Q: Did you have to compromise anything because you were trying to shoehorn the project into V8's API?
A: There have problems that lead to re-writing some elements.