Following is a quote from Microsoft’s announcement on MechCommander 2 Shared Source Release page with a few handy hyperlinks tossed in:
This is the Shared Source release for MechCommander 2. This release contains all of the source code and source assets required to build MechCommander 2. This release can be used with the Microsoft XNA Build March 2006 Community Technology Preview (CTP).
Update: A direct link to the End-User License Agreement for the MechCommander 2 Shared Source Release has been added at the bottom of this page in the “Related Resources” section. This allows you to view the terms of this release without downloading the entire installation package.