In addition the origin of Stallman's open source philosophy was a printer he couldn't use because of closed-source software. From the start it was about the rights of the users, not corporations.
https://www.free-soft.org/gpl_history/
> In the early years (1984 to 1988), the GNU Project did not have a single license to cover all its software. What led Stallman to the creation of this copyleft license was his experience with James Gosling, creator of NeWs and the Java programming language, and UniPress, over Emacs. While Stallman created the first Emacs in 1975, Gosling wrote the first C-based Emacs (Gosling Emacs) running on Unix in 1982. Gosling initally allowed free distribution of the Gosling Emacs source code, which Stallman used in early 1985 in the first version (15.34) of GNU Emacs. Gosling later sold rights to Gosling Emacs to UniPress, and Gosling Emacs became UniPress Emacs. UniPress threatened Stallman to stop distributing the Gosling source code, and Stallman was forced to comply. He later replace these parts with his own code. (Emacs version 16.56). (See the Emacs Timeline) To prevent free code from being proprietarized in this manner in the future, Stallman invented the GPL.