You're missing the point of GPL-style licensed Open Source Software. It's a matter of copy_left_, vs copyright. The difference isn't comparing the rights of GPL software writers/publishers vs the rights of movie publishers.
It's about the idea that software (and, for many, all digital media) should be free. The GPL is designed to "infect" other projects, by forcing them to be free if the GPL code is included. It's using IP/copyright laws to combat profiteering in software (and, in the case of movies, Blender releases a GPL'd movie every few years).
It's the activists' FOSS license, unlike the MIT/BSD/Apache licenses, which are just the literal definition of Free and Open Source, no strings attached.