Yesterday, on the bus, I found out an otherwise unassuming acquaintance who works at the local veterans' hospital, is a devotee of the VA's VistA health information system, and the MUMPS system that supports it. I knew there were people still forced to use MUMPS; I didn't know anyone actually enjoyed it.
The VA open sourced VistA while I was working in medical software. I spent a few hours typing inscrutable strings of strange characters into an only semi-responsive console before giving up with the conclusion that anything that esoteric wouldn't be much of a competitor to our product. Which is not to say our product actually worked, just that it was easier to install.