There's a story about a US astrophysicist grad student working on stellar evolution. A visiting Soviet scientist came to give a talk. At the end the student asked a question about one aspect of the talk, something like, how do you know the plasma is transparent to photons at that temperature? The visiting Russian just said "it is." Later, the grad student mentioned it, quizzically, to his advisor. His advisor pointed out that it was something that came out of nuclear bomb research.

I looked, but could not find that anecdote.

Did they attempt to open source the software?

IIRC, the code in question was written under an NSF grant, and probably not that hard to obtain.

Hopefully not