How closely are Mac OS X and BSD related?

Question

I read that Mac OS X and bsd are related. How closely are they related. Can Mac OS X software be tweaked and installed on BSD?

Answer 1

Mac OS X is one flavor of BSD Unix. As Borelaid already pointed out, that does not necessarily mean that porting Mac apps to other flavors of BSD would be easy or even manageable, much less so than between other common BSD flavors. Every one of them brings their own specifics, and OS X more than most.

Porting programs from other BSD flavors to OS X also involves work and does not always work (smoothly or at all), but is usually much more straightforward.