We've been dropping little hints about the name for months now - the MIME type for the browser plug-in in the Feb CTP was
application/ag-plugin and the script instantiation used a
new agHost(...) call. Ag (short for Argentum) is the symbol for Silver in Mendeleev's Periodic Table of Chemical Elements.
The .NET connection
Yes, Silverlight extends the reach of the CLR and .NET Framework to other platforms like the Mac! Details coming soon.