I'm missing something... if he can't get the door open how is this going to help?
As I understand his question its not the door that is stuck, but the latch. Undoing the hinges at the very least will allow jiggling the latch and it may allow removing the door without operating the latch.
Those old latches don't hold all that great in the first place, it shouldn't be real hard to rattle the door off with the hinges unbolted.
But I'll admit I haven't tried this approach. Last time I had the problem I spent weeks spraying the latch with penetrating oil and eventually was able to operate it. I was in no hurry so it didn't really matter.
