.NET Open Source

Microsoft published some of the .NET assemblies:

    * Mscorlib.DLL
    * System.DLL
    * System.Data.DLL
    * System.Drawing.DLL
    * System.Web.DLL
    * System.Web.Extensions.DLL
    * System.Windows.Forms.DLL
    * System.XML.DLL
    * WPF (UIAutomation*.dll, System.Windows.DLL, System.Printing.DLL, System.Speech.DLL, WindowsBase.DLL, WindowsFormsIntegration.DLL, Presentation*.dll, some others)
    * Microsoft.VisualBasic.DLL 

The CardSpace related part don't seem to be in this list.

There are some part of the CardSpace documentation where source code would really help to build interoperable parties.
On the other hand: than I would have to think about the reference license. Which I don't want to do.

Original post where I found this information (german).