I've always pronounced it "jif" and people always give me weird looks as if I was wrong....now I can show them this and be like "I WAS RIGHT MOTHER FUCKERS!!!"
That's the giraff mnemonic syntax, for memorizing veldt animals. And I do pronounce the Giraffe Interchange Format as JIF, it's a handy way to differentiate between the two when talking. Mixing them up leads to endless confusion.
They pronounced it "jif" so they could use the tag line "Choosy programmers choose GIF" which was a play on Jif peanut butters popular tag line at the time. So it has nothing to do with how the acronym _should_ be pronounced and all to do with marketing.
Screw marketing.
Screw marketing.