These different kernels do not use the same libc. In particular, BSD derivatives are using a BSD libc, while Linux and friends are using glibc (or some cousin).

These different kernels do not use the same libc. In particular, BSD derivatives are using a BSD libc, while Linux and friends are using glibc (or some cousin). I'm not certain which libc the others are using, but they are likely separate forks as well.