As far as I know, the first non-commercial work was done at the Naval Post Grad school with V6. I have never seen the code for it, only a paper, so I don't know too much about it to comment.
I tried to find the code a couple of years ago, but no joy. And the timing suggested he may have started with/used V5, since the paper is dated June 75 and V6 was released in May 75.
Thanks - that makes sense. As I said, I never saw the code, and again, it agrees with my observation that this was 'pre-USENIX,' particularly since I believe that those folks are in CA and the original USENIX people were in NYC and Boston folks, so they would have been less likely to be a part.