Scott Guthrie posted the announcement on his blog today. It's a 'read only' license with a few other limitations, but in general this is a great thing for .Net developers. Sometimes you're just curious, sometimes it's really important to see what goes on at the deepest levels. It really makes me wish - again - that MS would release the source code for SQL Server, or at least the optimizer, the one black box that so many of us spend time trying to understand based on what we see happening, rather than truly seeing why it made a decision.