Despite the FSF's word games with "copyleft", the GNU GPL, Creative Commons, and F/OSS licenses rely on legal copyright protections in order to work. It's the copyright holder who reserves the right to license the software by those terms.

https://www.gnu.org/philosophy/free-sw.html

https://creativecommons.org/faq/#is-creative-commons-against...

Closed source is protected in other ways besides copyright. Trade secrets, confidentiality, NDA, proprietary ownership, obfuscation, and in the case of hardware, big globs of epoxy and other countermeasures to ensure nobody can get in and reverse-engineer it.