Microsoft is open sourcing the .NET Framework

Scott Guthrie announced today that Microsoft is opening up the source code for the .NET Framework library with the release of the .NET Framework 3.5 and Visual Studio 2008 later this year. Microsoft will begin by offering the source code (with source file comments included) for the .NET Base Class Libraries (System, System.IO, System.Collections, System.Configuration, System.Threading, System.Net, System.Security, System.Runtime, System.Text, etc), ASP.NET (System.Web), Windows Forms (System.Windows.Forms), ADO.NET (System.Data), XML (System.Xml), and WPF (System.Windows).  It will then be adding more libraries in the months ahead (including WCF, Workflow, and LINQ).  The source code will be released under the Microsoft Reference License (MS-RL).

Source: Scott Guthrie