Oh yeah, you can run Class Viewer as an applet. For a while I did have it up at my SourceForge site as an applet but I wasn't sure that was ok, and didn't want it to turn into some kind of reference site.
But anyone can just throw it on a webpage, maybe with their own code's javadocs bundled up in the jar file so that they can access their class information from the web.
Class Viewer is a hybrid app--it runs on the desktop or on the web, with less functionality from the web.
I think hybrid apps are the future of app development.