No big deal, really. Others have actually done it before me.
But it is cool.
All I had to do was install the OpenJDK package (in my case version 8), thus:
pkg install openjdk8
Then I restored my /opt/opendj from backup and renamed to /usr/local/opendj (there is normally no /opt on FreeBSD). Had to make a change to the path for JAVA_HOME in $DSHOME/config/java.properties and then ran $DSHOME/bin/dsjavaproperties to apply:
Then su’d to opendj and ran $DSHOME/bin/start-ds.
[04/Nov/2014:06:30:07 -0500] category=CORE severity=NOTICE msgID=458891 msg=The Directory Server has sent an alert notification generated by class org.opends.server.core.DirectoryServer (alert type org.opends.server.DirectoryServerStarted, alert ID 458887): The Directory Server has started successfully
The init script does not work yet. Still re-learning how to port the Linux-centric script created by the OpenDJ utilities to FreeBSD.
I did not change the server owner or listening ports for OpenDJ. The former continued to be the local opendj user and group, the latter 1389 for LDAP (and LDAP over TLS) and 1636 for LDAPS. I look forward to figuring out how to forward inbound ports 389 and 636 to the OpenDJ listeners the way I did with iptables on Linux.