Open source means software that is open for use by other developers/projects, and therefore gets battle tested in many contexts.

If #Bitcoin was closed for use, but merely "source viewable", the project would have failed or been replaced by software that was free (as in freedom).

Don't let sleezy projects gaslight you.

"Open-source software (OSS) is computer software that is released under a license in which the copyright holder grants users the rights to use, study, change, and distribute the software and its source code to anyone and for any purpose."