Re: Correct me if I'm wrong, please: @INFINITY -1
Back when UNIX was effectively a Bell Labs. internal project, with educational institutions given source code access for the cost of the media, a lot of this UNIX software you talk about was actually written by people working in the educational institutions. As such, they almost certainly did not own all of, or even very much of the work they did (most institutions take part or all of the rights to inventions by their employed staff, with research sponsors taking some of what's left).
Back in those days, it was much more simple to write something for your local use, and make it available for free or media costs to other educational institutions, rather than trying to monetize it. As such it was often provided with little or no license other than something like "free to use for educational institutions". This effectively meant that by sharing it, you had already lost control.
RMS himself understood this. In order to be free of these restrictions so that he could assert his right to make software freely available, he resigned from MIT shortly after starting the GNU project.