Section SEE ALSO: In FreeBSD there is no launchd(8)
I've addressed this in the upstream repository: https://github.com/openbsm/openbsm/commit/4a6074c356cfe9494f34d8b275d03971996a5740 This will make it into FreeBSD with the next OpenBSM release, which will come within the next few weeks. Thanks!
In RELEASE-10.2 it can still be found in man 8 audit.
I just imported a new OpenBSM version into HEAD (r292432), which will be merged to 10-STABLE before 10.3-RELEASE. The new release contains annotations to make clear when a manpage is only available on OS X. Thanks for the report!