FinCEN's guidance on crypto business models: are you a money transmitter?
davidgerard.co.uk
davidgerard.co.uk
The only thing I would add to clarify money transmission as "transmitting value that substitutes for currency" is that exchanging funds for goods (normal commerce e.g. buying a coffee with credit card / cash / apple pay / stablecoin) is probably not considered money transmission. But I'm not your lawyer.