They open sourced the compiler and some stuff a while back but now are open sourcing the server portion of the APIs.
http://arstechnica.com/information-t...inux-and-os-x/
They also announced Visual Studio Community Edition which is not hamstrung like Express, free for small teams.
Being able to run production grade .NET server code on Linux is a good thing IMO, there's been a few projects in the past that we've not got involved with because the server stack was pure MS.
Microsoft open sourcing .NET, offering free Visual Studio, world upside down
