Some of Apple is open too, but they are not bound to the GPL license like Linux, that allows foreign governments to rename them, resell them, etc., without any return revenue to the US. "Red Hat" Linux from North Carolina allows the Chicom government to rename their product "Red Flag", and remarket it in Asia, potentially costing the US that entire emerging market from all US software vendors, as China has named "Red Flag" the official operating system of the PRC. And why wouldn't they, if some idiots in the US are willing to give them complete and total control of their new code and features for free?
As far as it applies to this discussion, Apple's Darwin license is effectively the same as the GPL. China can, without payment to Apple, download Darwin, modify it, and redistribute it. There you go, a fully functional BSD variant every bit as good as Linux.
Learn you licenses before you start talking about them.