Richard Stallman, is responsible for the free software movement. He started it while he was with GNU Project. Without his movement Linux wouldn’t be here today. His philosophy was whoever is at the computer should be able to do whatever they want, the user who used the machine the day before shouldn’t be able to tell you what your experience should be today.
Microsoft was one of the first companies who did not allow public access to source coding, making it proprietary. Richard thought this act made the company a bad person. It hurt people from doing useful things so he set out to change it by starting the Free Software Foundation.
GNU= Gnu’s not Unix. Play on words because Unix is proprietary. Free software doesn’t refer to price it refers to freedom. Copyleft is Copyright flipped over, it allows changes to be made and distribute but when redistributed it must meet the terms that it must still allow changes for the next person.