article which link been posted by Benson misleading. MtGox got registration for 409 money transmission and 499 other. Perhaps 499 other will fit into electronic money exchange.
Doh!
Mt Gox registered with FinCEN as a money service business (MSB) that serves as a money transmitter.
They did not "get a license".
There is no such thing as an MSB license.
There are some states that require Money Transmitters to be licensed. Mt. Gox has not received any money transmiter licenses yet, apparently, and it isn't known if they'll even do that (it is very expensive to do).
Has been clarified by Stephen.