IBM wasn't the only company or person developing software. Consider TeX, released before 1980. Is that open-source? See also https://en.wikipedia.org/wiki/His

IBM wasn't the only company or person developing software. Consider TeX, released before 1980. Is that open-source? See also https://en.wikipedia.org/wiki/History_of_free_and_open-source_software#Free_software_before_the_1980s https://en.wikipedia.org/wiki/History_of_free_and_open-sourc... , which includes a link to the work by SHARE - https://en.wikipedia.org/wiki/SHARE_(computing) https://en.wikipedia.org/wiki/SHARE_(computing) . > In 1959 SHARE [a volunteer-run user group for IBM mainframe computers that was founded in 1955] released the SHARE Operating System (SOS), originally for the IBM 709 computer, later ported to the IBM 7090. SOS was one of the first instances of "commons-based peer production" now widely used in the development of free and open-source software such as Linux and the GNU project.