Exactly. AT&T Unix was the quintessential example of source-available software. Companies and institutions could get licenses for the Unix source code, but th

Exactly. AT&T Unix was the quintessential example of source-available software. Companies and institutions could get licenses for the Unix source code, but they weren’t allowed to redistribute it, and it certainly wasn’t free. If I recall correctly, while it was originally only $99 for academic institutions, the price went up by orders of magnitude after the breakup of AT&T (before the breakup it was prohibited from monetizing Unix due to an agreement made with the US government when AT&T was involved in an anti-trust case). We wouldn’t have our modern BSDs if it weren’t for people being frustrated with source-available Unix. BSD initially started out as essentially a collection of additions to AT&T Unix. Eventually after the divestiture of AT&T and the resulting dramatic price hikes for Unix source licenses, the Berkeley developers embarked on a campaign to replace AT&T source code to develop a fully open source Unix. They beat GNU to the punch (see GNU Hurd), only to be stymied by lawsuits from AT&T.