I don't know your plans, but if banks (or Fiserv or FIS) are the ones paying you for a license to your front-end, then they are your customers. End users are the banks' customers, and in whatever contractual agreements you end up signing, based on my experience, the banks and their regulators will make absolutely sure you know that.

Also, you should change your name now before the regulators make you. Consumers think that financial companies with "bank" in their names are banks.