What more is there to say?  Microsoft opensourced Roslyn (.NET Compiler Platform), source is avaiable on CodePlex!!!

It's fantastic news, to quote Eric Lippert

What astonished me was that its not just a "reference" license, but a full on liberal Apache 2.0 license. And then to have Miguel announce that Xamarin had already got Roslyn working on linux was _gobsmacking.

It's a huge step, and something I hope Microsoft does more of.  I can't wait to find some time to dig into this code, and see how it all works.