Is it possible to create a complete client side application using HTML 5 (it will embed chat clients, stock ticker) + JavaScript, and then bundle is with underlining Firefox 3.5 engine, so that user can install it as a desktop app on Linux, and then it runs in its own window using firefox 3.5 engine. The app will store everything in local storage - like url, usernames etc, and will not interact with any local server.

It would pure HTML5 + JavaScript based client web app which would be packaged, and can be installed or launched from startup scripts.

Or instead of using firefox 3.5 engine, we can use Mozilla Prism to convert it to web app, and then bundle it.