Bounties can be placed by nations AND subfactions. They may place bounties on people who act against their interests.
For proof: https://vendetta-online.com/x/msgboard/14/31560.
Bounties may be taken by anyone with a Bounty Hunter License, which may be acquired from the local Marshal NPC in the various Capital sectors. A Bounty Hunter License requires Combat, Heavy and Light weapons license levels of 4 or greater, as well as a one-time fee of 50,000c. Once the Hunter license is acquired, any person with a Bounty on their head may be attacked. Dispatching them successfully will result in the reward being instantly transferred to the Hunter's account.
IMPORTANT FACT: Having a bounty placed on your head, and being killed by a character with the Hunter license, will result in a 1 percent loss of skill in all areas (Combat, Light Weapons, Heavy Weapons, Mining, and so on). Again, being the "victim" of a successful bounty will lose you 1% across all skill types.