IIRC, the format for Silverlight output was well documented, and open. It was a zip file with a manifest, assets and JS. The down side is they didn't get the penetration. Silverlight was FAR closer to what I'd hoped that Flash would have become when Adobe bought Macromedia. Adobe was really pushing SVG before that, and my hope was that flash content would become a zip, with assets and a manifest, where 2D assets were svg, and the tweaning was something similar to CSS.
Either could have been adopted. Would still love to see an HTML "package" format that was similar, where the whole content and assets could be downloaded as a single container, and run offline easily like flash could.
Only Silverlight v1 was Javascript based. From version 2 upwards a small CLR implementation was the runtime. It allowed .net languages (C# and F# mainly) to be run.
Silverlight was not open source though and it was not cross platform either. Having Silverlight/.Net and Flash/Flex/Air open sourced and competing would have been great, as a copmpany I would have made money from the IDEs and tools, why you need to keep it proprietary and then kill it.
Silverlight was available on Mac and Windows, and Moonlight was available on Linux. Again, the plugin itself didn't have to be open-sourced, the format was, which is why Moonlight worked.
In my opinion having Linux support done by community and lagging behind in features and in release scheduling is not cross-platform, Flash had the advantage in this point, Adobe AIR also worked on linux until a point.
Do you think that having this platforms opened source would help or not the adoption? Looking at Java I see it is still going strong with plenty on languages, tools and libraries/frameworks still going strong.
My entire point wasn't that Silverlight was/wasn't open sourced... it was that the underlying structure was FAR closer to what I thought was a good package structure, compared to .SWF
Either could have been adopted. Would still love to see an HTML "package" format that was similar, where the whole content and assets could be downloaded as a single container, and run offline easily like flash could.