I’d just like to interject for a moment. What you’re referring to as BSD, is in fact, FreeBSD/NetBSD/OpenBSD, or as I’ve recently taken to calling it, BSD-based operating systems. BSD is not an operating system unto itself, but rather another free component of a fully functioning BSD-based system made useful by the BSD kernel, libc, and other essential components of a complete OS.
Many computer users run a modified version of the BSD system every day, without realizing it. Through a peculiar turn of events, the version of BSD which is widely used today is often called “FreeBSD,” and many of its users are not aware that it is basically the BSD system, developed by the FreeBSD Project.
There really is a BSD, and these people are using it, but it is just a part of the system they use. BSD is the kernel: the program in the system that allocates the machine’s resources to the other programs that you run. The kernel is an essential part of an operating system, but useless by itself; it can only function in the context of a complete operating system. BSD is normally used in combination with the GNU operating system: the whole system is basically GNU with BSD added, or GNU/BSD. All the so-called “BSD” distributions are really distributions of GNU/BSD!