I would imagine that otherwise if you happened to have a client who derived income from sex trafficking that would present a problem. Or even a client's client

I would imagine that otherwise if you happened to have a client who derived income from sex trafficking that would present a problem. Or even a client's client. E.g., Paypal might be deriving income from sex trafficking if a sex worker takes payment via it. Not that the rest of the license is unworkably vague, but that limitation at least makes some sense.