Although, the term "Broker" implies a certain level of accredidation and professionalism. Brokers, in every other industry, requires certification and implies a given set of assurances and actionable repudiations.
Calling one's self a "broker" may be misleading in the case of domains.
Sure, the buying and selling of some item is taking place, but that would simply fall under the title of "Salesman" in most cases and "buyer" in others.
When I was in Grade School, I used to haul irrigation pipe through the neighbors field during the summers to earn some cash... we called ourselves "Moisture Control Technicians".
Why? To make our jobs sound better and more important.
Some "squatters" are nothing more than opportunisists and resellers. Others are just businessmen/women that buy and sell many things... "Traders" I would call them. Then there are some that are truly "Brokers".
The vast majority, if we were being honest, are nothing more than day traders or domain investors/developers.
Of, if you REALLY want to be creative....
"Digital Communications Managment and Procurement"
GoPC