Mm, even that I don't think words like "licensing" is a concept that exists in Eorzea at the time being. It's important to put Eorzea's current era with its RL historical analogue for such things (especially that SE don't seem to be writing the non-fantasy aspects of the universe with a contemporary bias). I'm pretty confident anyone can who can successfully apprehend a wanted criminal and  turn them in to the Brass Blades, Wood Wailers, Yellowjackets, Grand Companies etc. can call themselves a bounty hunter.
quick edit: I reckon a "prolific" bounty hunter is someone with a well-established reputation and known among those authorities, not someone with a 5-star license or what have you :E
quick edit: I reckon a "prolific" bounty hunter is someone with a well-established reputation and known among those authorities, not someone with a 5-star license or what have you :E