Silverlight is Microsoft's Rich Internet Application browser plugin, which allows you to script the browser with Python! It's great fun to program, but the Microsoft version only works on Apple Mac OS X and Windows computers.
Microsoft has collaborated with the Mono team to produce a Linux version built on Mono; providing them with tests and multimedia codecs - plus open sourcing some of the GUI controls.
Moonlight 2.0 Preview is a preview release of Moonlight targeting binary compatibility with Silverlight 2.0 applications and working as plugin for the Firefox browser:
After a loving incubation period, the Moonlight 2.0 preview, an open source implementation of Microsoft's Silverlight for Linux has been released.
This is really the release I have been looking for since Microsoft first introduced Silverlight 1.1 and ever since our 21-day hack-a-thon to bring Silverlight to Linux.
This is the ECMA VM running inside the browser and powering C# and any other CIL-compatible languages like Ruby, Python and Boo. You can use Moonlight/Silverlight as a GUI (this is what most folks do) or you can use it as the engine to power your Python/Ruby scripting in the browser.