I am 99.99% sure one would need a money transmitter license in the US to exchange bitcoin. Running a bitcoin ATM can also be classified as an exchange by Fincen
Just to clarify the terminology, FinCEN does not
license money transmitters. It's the money transmitters who
register with FinCEN. Licensing happens at the state level where many have not taken any position on Bitcoin yet. So yes, you must be registered with FinCEN, but do you have to be licensed as a money transmitter in your state? It depends...
More detail on my blog here...
http://blog.atlantabitcoin.com/us-bitcoin-atm-regulation-101/