It looks like JDS (Java Desktop Environment) is a window manager or something similarly. So to answer your first system, you can't install ANY applications on JDS since it isn't an operating system (as far as I can tell). I don't think this is the correct use of the terminology here. Of course, perhaps we are each using the word "install" in a slgithly different sense. It seems like you can install any packages that are allowed by the underlying Linux distribution. If JDS is a Window Manager as I guess it is, then it should be able to run any X applications. This also means that it shouldn't interfer with any console-based applications, so if you can open a terminal, you can use any of the common command-line apps (like vi and mysql) just fine. I'm not exactly sure how it will interact with KDE. I suspect that you would have to choose between one or the other.