I investigated a bit more this morning...
Your are right: it only happens with copy contents is set to true.
When the content has been copied, the remoting client, which is starting a {{StreamServer}} instance, is closed, but the {{StreamServer}} is still alive. It doesn't get the StreamHandler.CLOSE from the server side and the connector is not stopped explicitly on client side, even if client.close() is invoked after every action called on the {{StreamingDeploymentTarget}}.
The {{StreamServer}} will be removed upon finalization...
I don't know for now, if the client side (deployment) is responsible for closing the {{StreamServer}} or if this is something that came with jboss remoting 2.5.3 .
Other remoting threads are daemon threads, but I think, making the {{AcceptThreab}} daemon would only heal the symptom... ;-)