Microsoft extended Silverlight's reach by millions today with the release of a free Symbian run time. The release comes nearly two years after the project 's beta code was delivered, and brings Silverlight to Nokia S60 5th edition phones. Whether Silverlight's arrival on Symbian can actually help position Microsoft's Silverlight platform as an effective foil against the growing popularity of Android and iPhone among developers is another story.

There is a compelling case for mobile Silverlight application development: developers can reuse their existing .NET programming skills and can take advantage of the platform's rich UI and media capabilities. Silvelright is cross-platform, so applications developed for Windows Phone 7 (when it's actually available) could be ported to Symbian. Microsoft has not yet announced support for Android, but executives have not denied rumors that a project is happening. Regardless, Mono is an option for Android developers whether Microsoft decides to play in Google's backyard or not.

That leaves Apple as the odd one out; it does not permit runtimes on iOS. That's interesting not only because of the competitive dynamics of Apple Vs Microsoft, but Microsoft is being far more open than Apple. Android is arguably open source, and Symbian is the only major open source smart phone OS. Who would have thought that Microsoft would be on the side of developers while Apple lays down restrictions? I guess that the proof will be in how good the apps really are.