There is a bounty board on top of BB
Yes there is, but it is a shallow imitation of the OSI-style bounty system. The current system requires you to get the poster's permission to turn in the head and each bounty is individual, rather than racking up for additional murders. Take a look at the summary on Stratics.
http://uo.stratics.com/content/reputation/bounties.shtmlThe difference I'm emphasizing between the two systems is the reward. Currently, if an anti takes a bounty, the most common gold reward is low 1000s. If anti-PKs work as a team, they will have one head to turn in and will have to split the purse. Whereas if the bounty accumulated with time and was contributed into the millions, there would be stronger incentive to hunt a murderer down, solo or as a team.