FreeBSD uses FreeBSD init and Mewburn rc. Mewburn rc is somewhat different to van Smoorenburg rc. It has a huge library of standard shell script functions, and the actual rc files that ship with the operating system, and accompany packages, sometimes boil down to a few shell variable assignments and then an invocation of one of the shell library functions that does everything. This is not universally the case, however, and there are some giant exceptions.
The TrueOS people have replaced Mewburn rc with OpenRC, retaining the FreeBSD init as far as I am aware. I suggested to them back in January 2017 that since OpenRC has s6 integration, they might do well to add s6 to that to gain full service management. I never received a reply. I haven't heard that Laurent Bercot was contacted, either.
