The Copyright That Wasn't?

I was thinking about the ghosts of UNIX the other day, not in a supernatural sense, but wondering who actually holds the copyright on ancient UNIX? It's a question that seems straightforward, but asking it is like pulling a loose thread on a historical tapestry. Pull it, and you don't get a neat answer; you unravel a story of academic collaboration, corporate warfare, and two lawsuits that, when…