Prism, which is based on (or used to be called?) WebRunner is basically a tool for making a simplified standalone program which is basically a web browser (FireFox) locked to a specific website or service, with a simplified user interface.
It has some interesting possibilities from a developer's standpoint. Coders have actually been able to build applications out of the mozilla framework, including the browser component, for a long time.. But this seems to be on a course to streamline that process.
My only real concern is the huge memory footprint of firefox and startup time, etc.
Mozilla Labs is launching a series of experiments to bridge the divide in the user experience between web applications and desktop apps and to explore new usability models as the line between traditional desktop and new web applications continues to blur.
Unlike Adobe AIR and Microsoft Silverlight, we’re not building a proprietary platform to replace the web. We think the web is a powerful and open platform for this sort of innovation, so our goal is to identify and facilitate the development of enhancements that bring the advantages of desktop apps to the web platform.
The first of these experiments is based on Webrunner, which we’ve moved into the Mozilla Labs code repository and renamed to Prism.