Screaming Penguin - Source Does Matter

Check out OpenLazlo. This is an Open Source release of the Lazlo Systems product. This is basically a system that seems much akin to Macromedia FLEX, but without the $12,000/CPU license fee.

Like FLEX, the Client Components are built it Flash, so you have a good deployed based of supported clients. It runs as a J2EE presentation server app, where you output XML from you app and their presentation server builds the SWFs and sends them along to the clients.

Java.net has an intro article by one of the developers.