"I was told in school (in 1985) that if I was ever lucky enough to have access to the unix source, I'd find there were no comments. The reason, I was told at the time, was that comments would make the source code useful, and selling software was something AT&T couldn't do due to some consent decree. I've never been able to verify this story, but it came from someone who started with v5. Sadly, he passed away 15 years ago, or I'd just ask him again..."


Ah, the consent decree.   The basic idea of the consent decree was to prevent AT&T's regulated monopoly from giving it an unfair advantage in other areas.   And, since the regulation guaranteed a rate of return, certain restrictions were put on the ability of AT&T to do business outside of the telephone arena.  In particular, one requirement was that AT&T must patent anything they did that was patentable.  And furthermore, they must license that patent to all comers at a "reasonable" rate.

The decree was signed in 1956.   And then, along came software!  AT&T foundi itself required to patent software inventions at a time that nobody was sure what that meant, or whether software was even patentable.  There were some very strange patents, or at least patent applications, that came out of this.  I remember an algorithm for generating permutations that was recast as a relay computer because that was probably patenable and, if so, AT&T had to do it. 

Also, the mindset of AT&T was to plan in 20 year timescales, and they had trouble understanding the increasing speed of software innovation.  The patent department's attitude about a lot of the issues of Unix licensing, etc., was basically to wait 5 years until there was some precedent before acting.  Meanwhile, when they took an interest they would issue some directive, often to reverse themselves several months later.  I remember before one of the releases we had to make sure we had a copyright notice on every file, only to be told six months later to make sure that we removed all copyright notices from all files.

One run-in that I had with the legal team happened just as Unix and C were beginning to become popular, and some new C compilers were appearing.  I made a strong appeal, with the support of my management, to release the front end of PCC (or at least the Yacc grammar for C) into the public domain, to try to encourage some consistency in what we intended to be a portable language.  Meetings dragged on for months, and we were finally told no.   I don't know whether, had I been successfu, we could have avoided all the ANSI / Posix confusion that came later, or at least limit the number of incompatibilities that rapidly appeared in "C" compilers.  But it might have helped...

Steve