The answer is Eclipse, Java, the JVM, and Swing. Works great on Linux. I even think recent versions of Swing are coded to OpenGL for graphics acceleration.
You know what they say, Write Once and Run Everywhere (meaning Gnome, KDE, XFace, etc).
This is what I was thinking too. The problem, IMHO, is Oracle. I think they've scared everyone into thinking that the JRE will be limited in some way and legally encumbered so that they can monetize it. I'm not sure that's in their best interest.
Still, it's currently the best option for cross platform compatibility. Unfortunately, they never really figured out how to make Swing easy (and I say that after writing 1.3 million lines of code over the last 12 years).Oh, and while we're at it, date/time as all screwed up as is BigDecimal! Oracle, please, you can't be serious.