GNET is an ECN (Electronic Communications Network.) It is not an individual MM, but rather an electronic board, a forerunner of what the future might hold, where traders make their offers and bids sans MMs.
An ECN is a computerized order matching system used to display and execute limit orders. How does it work? An ECN is a matching service set up to match buy and sell limit orders. However, if there are no buy orders for a particular stock displayed on an ECN, an investor who places an order to sell that stock has to wait for a matching buy order to come in before an order execution can take place.