Yahoo! News - Microsoft Posts First Source Code Under Open Source License: "The source code posted to the Internet was for a tool set, dubbed WiX for Windows Installer XML, that targets developers building Windows installation packages from XML source code. These are the same tools that Microsoft uses internally to create installers for its products, including Office, SQLServer, and BizTalk Server.
Code for the tool set, which consists of a compiler, linker, a library tool, and a decompiler, has been posted to SourceForge.net, a hosting site for open-source projects and code. "