@joe It's a G, like in G-wagon. GPL stands for German Programming Language, and hence you have to obey strict rules. Or maybe it stands for Gangsta, not quite sure, but it would still be dangerous to call them J's.
@joe It had never previously occurred to me to pronounce it as anything other than "gee pee ell", but now that you've brought it up, it immediately becomes another front of the GIF pronunciation wars and so now I have no choice but to stridently insist upon "gipple" for the rest of my days.