a) Requirements. 

UCD-SNMP, v.3.2 ( at least i compiled with ), or,
may be some older (either where it was cmu-) version - 
snmp modules depends only on api, which had not changes.
You can get ucd-snmp at ftp://ftp.ece.ucdavis.edu/pub/snmp,
or at the nearest FreeBSD mirror in /pub/FreeBSD/distfiles

b) Compatbility.

The project started at FreeBSD 2.2.1 with gcc 2.7.1. 
and compiles here successfully. 

I think, it will be really easy to compile it under 
OpenBSD/BSDi. 


c) Installation notes.

Get and compile ucd-snmp. 
Edit Makefile.inc to say, where the libraries and includes of
ucd-snmp. 
Edit src/defines.h to define, where the default configuration 
file and logfiles must be written.
make
cp hqmon.conf.example hqmon.conf and edit it (Well, there are about 
no documentation at all, but.. ).
mkdir logs - the program is still so stupid to dump core when
it cannot write logs.. 

nohup ./src/hqmon &
chmod go-rxw nohup.out - there can be some output of resetscripts
in with passwords etc.. 

d) Running. 

There will be some files in log directory: 
problems.txt, flaps.txt and status.txt must change every POLLINTERVAL
seconds to show, what happens with your network. 
Also, there will be outages.list and debug.txt, which will 
increase-only.