karma plugin

Are there any users of the karma plugin out there?  I've been trying
to set it up, and so far failing.  When I enable it in my plugins
file, qpsmtpd fails to start.  The last line in the log, and the only
thing that looks like it's trying to start up karma is

Sat Jun 06 15:13:24 2015 g2[7780]: karma hooking pre-connection

I've googled around a bit but come up empty.  Is there something
special about karma that I should be doing?  Other hints on how to
debug where it's going off the rails?

TIA...