Again I agree with much of what you said.  But there are a couple of things your are forgetting....

On Wed, Feb 7, 2018 at 10:13 AM, Theodore Ts'o <tytso@mit.edu> wrote:

Well, MIT actually had multiple AT&T Licenses which did *not* have the
mental contamination clause. 

I fear, you are

​falling

 into an

 error of thinking about UNIX as the source cod

​e from Murray Hill as opposed the intellectual property -> i.e. an implementation vs, the ideas of how to build the a computing system.     The ideas was 

the point of the AT&T case

​ with BSD (as a number of people including some on this list have said -- AT&T was talking about trade secrets - which are ideas).  Note I failed to understand this difference myself at the time, most of us did also I fear because as you said -- we all just wanted Unix for a PC based platform that we own for ourselves.  However, I believe that understanding that difference is why the AT&T vs. BSDi/UCB case is so important to 

history,

​ and Linux's history in particular.​

What

​ doomed

 AT&T was they were required by law to release the IP (1956 consent decree)​

​ to any interested parties for a fair and reasonable license, but they had to continue to make their IP available to the academic community at no charge [I site the paper from one the law reviews that is really detailed, so I'm summaries the results.   Send me a message offline if you want to know more].  The fact is this worked out fine for technologies like the transistor.   People licensed it, AT&T never really made the kind of money, TI, Fairchild, etc did, but it was AT&T IP that used.  Folks took out a license and the wider electronics industry was born from that invention.

However, later 

AT&T's own personal start to publish papers and books about the

​ UNIX​

 

​IP

 in the open literature.  

​  It is these two acts together that the court said, meant that AT&T could not longer claim trade secret - they licensed it AND they told people about it.   They 'taught' the world - mentally contaminated us all - with their ideas.  Linus for instance says he had Maury Bach's book when he was building Linux and I have been lead to understand that Maury's book was used as evidence in the case ( as was the original 1974 paper).​ The point is once the IP was generally known, it was no longer a secret and AT&T could not claim same.   It also why the famous 6 files had to be removed from the implementation that BSD had.   Those were bases on the copyright ownership and AT&T was allowed to claim copyright (as many people like me, had expected them).  They just could not claim copyright on the parts that UCB had developed - even if they were the same ideas (IP) and AT&Ts.

So, I'm trying to be careful... this discussion was how did the Linux implementation of the UNIX IP displace the BSD implementation of the same IP?   I believe that it is a classic example of a Christensen disruption... a new market (PC based UNIX) was created nd people wanted something to fill it.   Linux was there to file it and did a great job and AT&T stopped any alternative (BSD on same) long enough, that it did not matter - Linux had filled the void well.   The sustaining 

technology

​ (BSD) stays with those that could afford it on their platforms (Sun, DEC, etc...)​

Stepping back a bit ... an interesting question is what about Sun's 386 attempts?  The original RoadRunner was a pretty slick machine.  But here is where I think they got stuck the same way DEC and other did.  They made their money on the HW but it was the SW that drove the sale.   So they wanted to SPARC et al.  So they kill RR.  By, the time of they retrench and Solaris/386 was released for "commodity HW", again - too expensive for the low end and they did not want the Intel chips on the servers to compete with their own HW.

Clem

As a minor footnote, I've always wonder about the SCO case being anything but a delay tactic against Linux.  Give the courts results from the AT&T vs. BSDi case, I'm personally surprised they got as far as they did.  I really would expected to be tossed out at the start (hut Im not a lawyer of course).   Clearly, the courts had declared that ideas were free and clear for anyone to use.   So how SCO could have claimed anything against anyone, I find hard to fathom.   Again the courts got it 

right

​, but it took a loot of time and effort for then to decide something that the another court had already decided.​