Alternative Implementations
The Mono team is currently developing Moonlight, a free and open-source implementation of both the Silverlight 1.0 and 2.0 runtimes.
The project is officially supported by Microsoft who,under an agreement with Novell, has made additional specifications, access to the Silverlight Base Class Library APIs, binary codecs and test cases available to the Mono team,none of which are available to other members of the public.