I've had this conversation many times (most of which took place in my own head, but some where real). I say it with a hard "g", as does almost everyone I know. I'm not going to go into why I say " gif" over "jif" since those arguments have been made over and over. But I will say why I'm going to continue to say gif, even though its inventor disagrees. It's great that that guy invented the thing, and he probably should be allowed to say how it should be pronounced (even if he's wrong). The fact is, however, the word is no longer his to control. A language is a living thing that evolves over time. Spellings change, pronunciations change, even meanings change. And English is especially fickle, as it's just a big amalgamation of other languages.

For instance, the capital of my home state is Pierre, named for a trader named Pierre Chouteau, Jr, who undoubtedly pronounced is name as "Pee-air" (hee-hee). But ask any SD resident how to pronounce their state's capital and they will all say "Peer," as will most anyone else in the US, because it has been fairly well established that the name of SD's capital rhymes with "gear." Are we all pronouncing it wrong? Compared to its namesake, yes. But it doesn't matter anymore because it is so deeply ingrained in the vernacular that it would be silly to try change it now. There are many other examples as well ("cough"[or any English word ending in "GH" and pronounced as "f"], "Zee" vs "Zed," or even the abhorrent case of another smaller town in SD, Sinai, the residents of which stubbornly pronounce "Sigh-nee-eye).

It's the same with "gif." Yeah, the guy who invented it pronounces it differently, but you can't really go against the vernacular. It's happened, it's a word now, whether or not the inventor likes it. It's part of something bigger, and we have to respect that. If people say something one way long enough, it's going to become accepted and eventually replace the old way, regardless of its linguistic historical accuracy. Keep in mind, "snuck" didn't used to be word and now it's in every dictionary. Likewise, I'll allow the residents of Sinai, SD to pronounce the name of their town any dumb-ass way they want, it's their town. And English is my language, and language is the most important way we interact with each other and try to understand our very existence.

Sorry for the ramble, I love linguistics and it's easy to get long-winded taking about it. Also, it's very obviously a hard "g."