Rover, Macs come with GCC, lol.
At least, mine did.
and yeah the topic isn't GUIs for Windows (which exist, but I don't bother with since I myself don't need it. I'm ok with the commandlining.). It's for Mac users. Mac users are always f*cked over. Though really, anything done with GTK should be doable on a Mac, seeing as a Mac is Unix and all.
I know WinVice had a GTK interface on Mac.
I sure as hell hope the Mednafen for Wii has a GUI, otherwise how would you even use it lol.