What does a masternode do other than transmit Darkcoin?
An administrator or an exchange that transmits convertible virtual currency to another person or location would be required to register as an MSB.
An administrator or exchanger that (1) accepts and transmits a convertible virtual currency or (2) buys or sells convertible virtual currency, however, is a money transmitter unless an exemption
applies.102
It appears that FinCEN is fine with masternode operation as long as the administrator registers as an MSB.
How many masternode operators are registered as an MSB?
Masternode does not transmit (= receive and send) coins.
That's your interpretation. I'm sure there are a plethora of Federal prosecutors and Judges that will see it differently. Masternodes are essential for anonymous transactions on the Darkcoin network so they could claim that they are involved in the transmission of funds. That's all it would take for an overzealous prosecutor to make a name for him/herself.
Masternodes are involved in the transmission of funds. That's enough.
It's entirely possible that without registering as an MSB you might get a visit from FinCEN for running a masternode in the United States.