I played with it a little while back but gave up pretty quickly. There was some system call that was missing under BSDs (poll maybe???) that seemed to be the main problem (whatever it was there was a similar alternative that could probably be used).
JEmpeg which is a java clone of emptool and emplode does work quite well under FreeBSD with the jdk1.2.2 from ports. The only problem is that the JVM appears to be unable to send a broadcast packet (same problem on Mac OS X incidentally) so autodiscovery of the empeg does not work. No big deal, just specify the IP.
Empeg's kernel download utility does compile and work fine under FreeBSD FWIW.
-Mike