> This would be accomplished by disseminating an operating system that is apparently inexpensive and easily portable, but also relatively unreliable and insecure (so as to require continuing upgrades from AT&T).

I remember watching a YouTube UNIX wars documentary that posits the exact opposite.

It argued that top brass at AT&T saw UNIX as a means to the telecommunications end, not a business in its own right. When it became more popular in the 1980s, it became obvious that they'd be bad businessmen if they didn't at least make a feeble attempt at making money off of it, so some exec at Ma Bell decided to charge thousands (if not tens of thousands; I can't find a reliable primary source online with a cursory search) per license to keep the computer business from getting to be too much of a distraction from AT&T's telecoms business.

That limited it to the only places that were doing serious OS research at the time: universities. Then some nerd at a Finnish university decided to make a kernel that fit into the GNU ecosystem, and the rest is history.