To be honest, this seems like a stupid fix to a non-issue.
There's already Latex, and the purists calling it Lateh only make it seem like they know and are ashamed.
Or Uranus being pronounced not as your-anus but urine-us. The "alternate/kid-friendly" option is just plain worse. It also teaches kids certain words are bad, which is a bad idea for a multitude of resons I won't get into.
I say keep GIMP GIMP, loud and clear. No need to be ashamed, because it isn't shameful.
Attempting to avoid this absolute non-issue by ingenious pronounciation or rebranding just exacerbates the issue.
It's called "GIMP" and not "Fuck Me then Go Out The Door". Wether or not GIMP was a moment of "funny humor" or not is beside the point. The "official" explanation is perfectly belieavable, and therefore suitable enough. Just run with it.
If an idiot asks "Why's it called like [insert-here]", just say it's a fucking coincidence and you don't care. Call them dirty-minded for bonus points.