The government of the port views taking ships and their cargoes from the skies surrounding the island as the only means currently available to them to survive, so they issue Letters of Marque to (at least partially) legitimise the practice.
The Rotmoons are among a number of non-human crews to hold one of these Letters of Marque, along side a number of other Greenskinz and Ogors. They are treated with contempt by most of the Ironfang Fleet because of their affiliation with the Port Mahóne authorities and it's "legality".
I have finished re-basing 7 more Rotmoons, including an Ogor Maneater, a Banner and a Drummer, so they are now a usable gaming force! They should make their Age of Sigmar début next week, when Viktor and I start our new mini campaign in Hysh, on his new desert scenery set.
These are the new Boyz:
(Apologies for the names if you speak Spanish!!)