Back when I was in University, we had an Amdahl mainframe with Unix running under VM. The directory structure included an awful lot of source code. I remember porting source for lex and yacc to my PC-XT running Borland's Turbo C. I assume it was licensed to Universities and source was included under an educational clause, though I'm not exactly sure.

I wonder which version of unix I was using. This would have been around December of '87.