Well, to tell the truth, I have not much idea about gps-bin innards - it was added by dholm, when he was overseeing Ada, before I took it back :). I just remember gps being quite picky and wanting its own version of everything (there might be another copy of gtkada, xmlada and may be something else lurking..).
I'll take a look, but likely I'll just add a more recent non-bin gps version when I have a time.
Looks like bug 75803 is still pending and this still unfixed, should we treeclean it maybe? :-/