You're using the word "Unix" where you should be using "Posix". Most Posix code will port relatively easily between different flavors of Unix, but when you start looking at GUI software the portability breaks down.
Linux GUI programs are usually written using a set of graphics tools that fall under the broad categories of GTK (Gnome) or QT (KDE), however they can be written in pure X11. Mac OS X applications are linked to proprietary Mac libararies (Quartz), which won't port to anything else. AIX used to be all Motif based, but I believe they've gone more open source since I stopped working with it. Solaris provides a lot of GTK/Gnome libraries and I believe Solaris 10 may even ship with a Gnome desktop.
But then when you add drivers for things like wireless cards underneath the GUIs, that's where you'll really run into problems. If the driver exists for linux, you're golden. If not, you better hope someone's working on it, because there are probably only a few thousand programmers in the world that could whip out a driver and even they would need detailed documentation on the hardware its API.
I guess that's a very long way of saying, probably not, and probably not by someone without experience porting software.
Last edited by brunson; 11th April 2007 at 12:22 AM.