I managed to build GENTle on Mac OS X 10.6, i386 architecture.
It seems to run fine, but when I import a GenBank file, I get a wxWidgets debug alert about an invalid tree item in DoSelect().
I think this is because in MyFrame.cpp on line 1140 subframe->initPanels() is called before mainTree->addChild(subframe,type)
If the order of the calls is reversed, it seems to work.
But I might be wrong, since I know only very little about wxWidgets.