"Microsoft's cross platform Silverlight browser plug in supports
Windows and Macintosh. The Mono project's Moonlight 1.0 -- an
implementation of Silverlight for the Linux desktop, and the only
open source version -- is in beta testing but the final code won't
be released for several weeks. Moonlight 2.0, which incorporates
many of the Silverlight 2.0 featutes, won’t be out until late
2009.
"Mono project chief and Novell vice president Miguel de Icaza
said there might be a workaround -- but it's not certain."