I don't see them as an option in the admin's payment provider list but I do see Ecommerce Templates in their list of integrators. https://www.gabpay.com/integrations
Hi Josiah A lot of payment providers used something called "Authorize.net Emulation" so that's a possibility. But it's also possible that they created their own integration scripts. But in either case, if you are interested in using them as a payment processor then just ask them.
Hi Josiah If they've created an integration then it will be done through the custom payment scripts, yes. But really, I would ask them first as it may be this is already done.