They are. Most companies using BSD-licensed software realize that it just makes sense to not release contributions back to the community. Having to backport whenever a new release comes out just to hide a couple shiny features quickly becomes very much not worth it. Netflix in particular is a major contributor in code, cash, and community, so saying the mods aren't free software is utter ignorance. The meme that only restrictively-licensed free software gets people to contribute back has frankly been debunked from here to mars and back.