I've recently been reading Ogilvy on Advertising by David Ogilvy, one of the most successful 20th-century figures in the industry, and while it's a bit dated (it was written 30 years ago) and, obviously, the subject matter is advertising, it's filled with excellent advice that's just as useful in all professional and personal contexts.
One aside that jumped out at me was "While we are on the subject of taste, I deplore the current fashion of using clergymen, monks and angels as comic figures in advertising. It may amuse you, but it shocks a lot of people."
I had honestly never really thought of it that way, but it's true. Religious people (that is, most people) find it hurtful and disturbing when you mock their religious faith. That might not be your intent, but it's kind of like 10 or 20 years ago when people used to explain that "by f-- I don't mean gay, just stupid." Just because you don't think or don't know what you're saying is hurtful does not mean that others aren't hurt by it.
If Mozilla had used terminology in their software that was offensive to women, or gay people, or non-Western religions, I'm sure they would alter it, and rightly so. If they called a copy-on-write library HolyCOW, and Hindus said they were offended by this name because it mocks their religion, I'm sure Mozilla would, rightly, change it. And they probably know enough not to use such a name in the first place.
Of course, "holy" is not a specifically-Christian term, but a concept shared by all religions, Western and non-Western alike. A devout Catholic, Muslim, Buddhist or Jew is equally likely to feel hurt and excluded when they see you comparing their beliefs to shit.
As for the other half of the name, the profanity ship has sailed in the broader culture and especially hacker culture, but it's also true that many people don't feel the same way, and nearly all of these people are deeply religious. I think it's reasonable to expect that religious people in the open-source community ought to accept that you or I will sometimes say "shit" for humor or emphasis, but it's also reasonable for them to expect we'll meet them halfway by not making them the butt of our jokes.
There are plenty of equally-funny "JIT" puns that don't come at anyone's expense; "GoodJIT," "JITHappens," "JIT'sTheBomb," and so on. I recommend using one of those.
I'm not a prude. I wouldn't scold you for saying "holy shit" (or "holy cow") in a conversation with me. I haven't scrubbed those phrases from my own casual vocabulary either. But, if someone told me I'd offended them, I would apologize and probably feel bad the rest of the day, just as I imagine almost any of us would. When you're participating in the open-source community, your audience is mainly strangers, with many different beliefs and backgrounds, whose first impression of you is formed by what you've written on the internet. So it doesn't hurt to be a little more careful.
 Hearing that speech a few hundred times, and maybe even giving it a couple, certainly didn't make high school easy for closeted me.
 Not that we shouldn't try our best to avoid needlessly causing offense whether it's to one group or many.
 And not only you, but the organizations, projects and communities you are involved with.
I hear what you say about my use of "idiots", but someone stirring the sh*t (yes, I can use (light-to-full) industrial language too, in its place) without any need, casually and semi-deliberately offending (or worse) many many others, is I think behaving idiotically.
BTW on your point : I am enraged when I observe people slandering two groups at once, casually: a direct target (A), by noting them as obviously as bad/gross/etc as assumed obvious horrible out-group (B). Gahhh!