Funny the things you think about at 3 in the AM.

There are two other things missing from Warner's timeline that I think are important.  A little about the clones and also about the commercial efforts (which turns out to be related as one might expect).

The first UNIX clone that I know about was a V6 version by Whitesmiths, called Idris, I want to say in 1977/78.   I believe that Michel's Gien's Pascal clone that he talked about a year later started out as V6, but morphed to V7 before he was done (and then later morphed again to become Chorus in a C++ rewrote).  Mike Malcolm's Thoth (which "Thucks" by the way, my wife threw out my tee-shirt years ago;-) was a pseudo V6 clone.   I don't think he tried to recompile V6 code, like he would with his later QNX efforts (and he wrote it in B, not C), but the model was V6 and he had seen and/or run V6 at Waterloo.

By the time of V7, the clones do start showing up. Minux which everyone agreed was original, as well as Mark William's Coherent, which in the end AT&T backed off. But as Dennis said at the time something to the effect, that it was not clear they had directly used AT&T sources to build it, as much as the authors clearly had seen/had access to UNIX operating and used it to build Coherent, plus they probably had seen the UNIX sources at some point (this was important later when AT&T would make 'Trade Secret' claims).

Idris is interesting in that when Plauger built it, he did get in trouble at the UDel USENIX when he tried to 'hawk it' and basically was booed (how he did was as much of a problem as that fact that he did it).  But by that point, there was another commercial UNIX available.   What's interesting is that there was not an official V6 redistribution license like there was for V7; so I'm not 100% sure I know how it was done and I would love to enlightened.

I know this much of the story.

As I mentioned before the first commercial user of UNIX was Rand Corporation in LA.  Al Arms of AT&T legal wrote the original $15K/CPU license for them.   I don't know how many of those licenses were made available, but I've always been under the impression it was under 10.  Like a lot of people at the time, this was when the 'glass tty' was just showing up in force and Rand updated/wrote a version of ed(1) called the rand(1) editor [IIRC, its still available as the 'grand editor' from Dave Yost].

Shortly thereafter, Peter Weiner and Heinz would create a company in Santa Monica called, Interactive Systems Corp (ISC) and they provided v6 and copy of the Rand editor for some commercial folks (FYI - ISC would later do the original 386/UNIX port for AT&T, IBM and Intel but that's a different story, and eventually Sun would buy them years later).   In fact, one of the things the folks at ISC did at the beginning was that they had worked with Perkin-Elmer and created a version of PE's 'Fox' terminal with modified ROMs that ran part of the Rand Editor in it [the Fox has a Motorola 6800 processor in it.  CMU had a lot of the standard ones because they were $750 in 1978 which was very inexpensive].   Anyway, what would eventually become the 68000 development team in Austin (Les Crudele, Nick Trudenick, Tom Grunner et al) used the ISC system and those modified Foxes as their development system.

What I don't know is how that license worked.   I think what happened was ISC was selling 'support.'   Motorola (or one of their customers) got a commercial license from AT&T and then got a support license from ISC with their additions.  But frankly, I don't know.