Comment by umanwizard

You’re making the common mistake of confusing the copyleft vs. permissive distinction with the free software vs. open source distinction.

GPL is copyleft. MIT, BSD etc. are permissive. But all of those are both free software and open source, which are essentially synonyms.

The reason so many people get confused by this is that some of the people who prefer copyleft licenses (notably the FSF) also tend to prefer the term “free software”, for philosophical reasons.