FreeBSD and OpenBSD switched to Xorg very early (in fact OpenBSD switched before most linux
distros did, and Theo de Raadt was one of the earliest and most vocal condemners of the
XFree86 licence change that prompted the Xorg fork). For technical reasons (relating to their
build system) NetBSD stuck with XFree86 in their base system, but have xorg in their package
system (pkgsrc) and will be removing XFree86 soon.