G.I.F = "Graphics Interchange Format".
Graphics = G and not J.
Can be argued "gift" and "ginger", but the english language word "Graphics" only has one correct way to pronounce and that starts with the sound of "Grrrr" not "Jrrr".
Doesn't matter what the "creator" of the image format says as its an acronym i.e. a shortened version of the full phrase, not a new word.