Its probably just part of the nonprofit campaign that lets this server run, if somebody is making money in their pocket a legal issue could arise.
Most MMO's don't allow it cause its competition for their game in a way, if their is cash being thrown around they want to be making it but seeing as how swgemu doesn't own or licensed to the rights to a starwars game and is only emulating one matters of money have to be handled carefully.
Just my guess.