Node.js is receiving Microsoft's support to move over to Windows. The logic behind this move isn't clear as the approach used by Node.js doesn't fit with anything else that Microsoft is doing.
Now Microsoft has decided that it is missing out and an it is going to help support Node.js under Windows. The plan is to create a binary that will work on servers from Windows 2003 to Azure. The work is going to be done in conjunction with the Microsoft Interoperability Strategy Team.
It is always worth asking the question of what Microsoft gets out of supporting an external project, but in this instance there is no obvious answer. Node.js doesn't fit into any of its current technologies and in fact undermines ASP.NET and the IIS web server. After all part of the appeal of Node.js is that it returns the task of creating the web server to the programmer.