Right, exactly what I said. They don't make money by market making. They make money by charging transaction fees, and on an access basis to their "algorithms" which are designed against analyzing the complex futures that they are the market maker for.

The incentive for users to sign up with them is to get access to "better" pricing for whatever commodity they pair the buy/sell orders for - but remember these are futures so its all betting, and so the algorithms don't really mean anything.