Where should the type information be: in tags and descriptors 457

That's correct, and at the same time it is correct that ÇBell wasn't allowed to sell it to just anyoneÈ -- you were allowed to buy what was essentially an evaluation (fully unsupported, as-is) license to the technology, that is the sources.

AT&T at the time was restricted by the 1956 Consent Decree (probably one of the most important events in the history of the 20th century), the terms of which that prevented AT&T from entering commercially, that is by selling products, the IT and other non regulated businesses.

However the 1956 rules allowed it to develop technology, including in IT and other non telephony-regulated areas, for its own use, and to license such technology, including patents, copyrights and so on, to third parties for research purposes or for commercial exploitation, which was not possible for AT&T to engage in themselves.

What happened therefore is that UNIX was licensed by a number of third parties, including Microsoft (for many years Microsoft was by far the biggest UNIX seller), and other now disappeared names like Interactive Systems, Microport, etc.

Eventually AT&T negotiated away the 1956 Consent Decree, and was then allowed to sell UNIX products directly, and they did not do it very well, as their core competency probably was regulatory capture, not technology or sales.