Call to action: Vote on User Voice for Silverlight to be open sourced http://visualstudio.uservoice.com/forums/121579-visual-studio/suggestions/5042512-open-source-silverlight 

For all intents and purposes Microsoft now views Silverlight as “Done”. While it is no longer in active development it is still being “supported” through to 2021 (source).
In today’s age of the “modern public web” with a variety of devices, Silverlight’s purpose no longer stands.

However there is still a section of the .Net community that would like to see further development done on the Silverlight framework. It has a nice collection of portable technologies allows it a small niche in the desktop environment. A quick look at some common request lists brings up the following stats:

Rather than letting Silverlight decay in a locked up source control in the Microsoft vaults, I call on them to instead release it into the hands of the community to see what they can build with it. Microsoft may no longer have a long term vision for it, but the community itself may find ways to extend it in ways Microsoft didn’t envision.
Earlier this year Microsoft open sourced RIA Services on Outer Curve http://www.outercurve.org/Galleries/ASPNETOpenSourceGallery/OpenRIAServices, it would be great to see this extended to the entire Silverlight framework.

We’ve seen what can happen with amazing technologies when they are released into the wild. e.g ID software released the Quake 1 source code to the community, it has since been extended greatly and ported to a variety of platforms. A version was even created for Silverlight http://www.innoveware.com/ql3/QuakeLight.html. Which makes sense as XNA running on Silverlight was a popular technology for students.

I’ve used games as examples of ways to extend it as that is what hobbyists usually latch onto first. But there are equal reasons why people still using it on internal LoB applications would want to continue to extend the core framework, e.g:

Silverlight still has a nice portable core of useful technologies, now is the time to start asking the question if it is time to Open Source it rather than let it mothball. There may be uses in the community for it now, in another 2-3 years its usefulness in the community would be lost. This also may be a great point to release Silverlight to the community.
Microsoft, let the community know if there is a way we can assist in making this happen.