Pirate Guild uses a rather complex bounty/reward system both for those who are fighter against the guild and the pirate players. Here is how it works. When you kill a pirate ship get a base sum of money based on ship's class. Moreover each pirate ships gets additional bounty for the mayhem they have caused. Maximal reward is capped according to ship class.
Same logic applies on police and military ships. PG will put a bounty on their head according to the damages they have done to the guild capped by ship class.
The plugin can spawn Bounty Hunters for most factions (Argon, Boron, Split, Teladi, Paranid, Terran). Those M6 ships will patrol across the map in look for ships with a bounty on their head (like mob boss, pg ships, and you).