Last week Jason Matusow, Director of Shared Source for Microsoft, has started a blog. In his second post - "More Open Than Open" - Jason gives a great overview of some of the different types of source licensing.
Microsoft has three Shared Source projects (WiX, WTL, and FlexWiki) under the Common Public License. A complete list of Microsoft's Shared Source Licensing Programs can be found here. These programs have only be designed with one goal in mind: meet the unique needs of the development community.
And if you're a C# developer looking for open-source projects, don't forget to take a look at the CSharp-Source.Net site. This site lists a large number of open source C# projects: from aspect-oriented frameworks to open source XML parsers. All developed in C# by the community and for the development community!