That's more of a toolkit problem. For most X apps, there's no way to figure out (for OSX) what part of the app is the Main Menu. And what functions to call when a drag/drop happens, there's no interface for it. Under X, every toolkit has it's own solutions. The only solution is to embed support for compiling to native Mac apps into the toolkit. There were projects to pull that off for KDE and Gnome, but somehow nobody continued working on them. I had the KOffice running first class on my Mac in 2004, and also Inkscape and GIMP a couple of years ago, but these native interfaces were buggy, and somehow there wasn't enough leverage to really finish them. Sad.