Thanks to the modernized MacOSX plugin the native fullscreen mode of Mac OS X (e.g. Mavericks) works nicely. The jEdit action
toggle-full-screen is rather useless, though: the window size is not correct wrt. the desktop, it is not really full-screen mode.
(Until recently it was unthinkable to get proper full-screen on that very special platform. Maybe the relevant MacOSX plugin functionality could be somehow integrated into the main codebase.)