Is this a first? Microsoft have released one of their internal development tools as an open source product, on SourceForge no less.
The tool is an XML based Windows Installer (MSI) creation tool, used internally within Microsoft by a hell of a lot of people, and it has now been released into the wild.
I look forward to trying out this product and seeing what it can do for me, should be interesting.
sourceforge.net project page
blog announcing the release