To run an snmpd plugin (shared object file) as part of the snmpd service just add the following line to the /etc/snmp/snmpd.conf file:
dlmod dosTFAgentPluginObject /home/desmond/.snmp/dostf-plugin.so
Or, replace the name of my plugin with yours. Then just restart the snmpd service:
sudo service snmpd restart
And Bob is your uncle. Hopefuly this will be a bit more robust than running it as a separate demon.
Addendum: it is more robust, and hasn't fallen over yet.