For the 2 people who don't read many blogs (or twitter), but do read this one, yesterday it was announced that ASP.NET MVC 1.0 is open source baby! "Free like Speech." and there are no restrictions to the platform either, the license is MS-PL which provides broad rights to modify and redistribute the source code.
The first question that was raised was "can I submit patches?" and the answer is no, however nothing stops you from going and creating your own copy (forking) and start modifying it and redistributing it like this guy has already done.
You can get the source code here.