Adobe and Facebook have announced that ActionScript 3, the language of Flash 9 and higher, is now officially supported by FaceBook along with JavaScript and PHP. Information about coding for Facebook with Flash is here, and the library itself is on Google Code.

MySpace has announced the MySpace Silverlight SDK which will be hosted on Microsoft’s CodePlex open source site. The focus of the Microsoft Silverlight work seems to be on wrapping the Open Social API used by MySpace in a C# library.

Note that there is already documentation on creating Flash applications for MySpace. On the Facebook side, here’s an intriguing fact: there’s also an Fb:silverlight tag, though the documentation remarks: “For now this feature has no functionality.” Fb:swf is better supported. David Justice has been working on a Facebook library for Silverlight. It’s clear though that Flash is more widely accepted and supported on both platforms, reflecting its maturity and broader acceptance.

Smart developers can already devise code to access the public APIs of platforms like Facebook and MySpace from a variety of clients; this is about making that easier. It benefits the social networking sites if a wider group of developers has access to its platform, and with the advantages of multimedia features; equally it benefits the plug-in vendors if their runtime works smoothly with the broadest possible range of services. Therefore we should expect more of this type of announcement.

It is interesting to see technology partnerships bridging political divides. Microsoft has a stake in Facebook, for example, while Google has a partnership with MySpace.

Perhaps the most interesting outcome may be more Facebook applications based on AIR, Adobe’s Flash platform for the desktop. The existence of AIR applications like Twhirl and Tweetdeck has significantly boosted Twitter; maybe it is now Facebook’s turn.