Last night when I instinctively typed 'man ascii' on OSX and it came up with that man page, and when I do 'ls -lsh |sort -n' to sort files by size _and_ also have the human readable sizes visible, I keep being reminded that OSX is still very much BSD under the bonnet, for me.
That's just the userspace on top of the kernel though, not the OS (IMHO), though it's difficult to decide where to draw the line. By your measure Debian/kFreeBSD could well be linux...
I know OSX is a valid and real UNIX, and the kernel is a mach/BSD hybrid, I'm just not sure I'd count it as a BSD when the question is 'Why is linux more popular than BSD?'. IMHO the question implies Open/Net/Free/Whatever BSD, not OSX. What makes OSX popular is a whole variety of things, many quite separate to the things people find appealing (or not) about the BSDs. IMHO, YMMV, etc etc
BSD is an operating system, Linux is a kernel, checkout the FreeBSD / OpenBSD / Darwin sources and you'll find a complete OS in the source tree.
Debian/FreeBSD isn't linux because it doesn't use the Linux kernel. I think there is more question as to wether most Linux distributions are Linux or GNU/Linux than whether Debian/FreeBSD is Linux.
If BSD is an OS then I don't think OSX is a flavour of BSD...
I don't disagree with any of what you're saying there, I just think it's a very grey area where you have multiple kernels and userlands, some of which are fairly easily interchangeable. And yes, most linux distro's are GNU/Linux (or at least something/linux) where Android/Linux is quite distinct.
