Robert,
I don't know much about them, they were just one of the six zillion I've found since I've been trying to find the perfect system for myself.
From looking at the source, it looks like the form information is emailed - naturally I can't see the script, but the demo form seems to email the response, and carry variables to direct the user to your payment processor.
That being said, it looks like it would be easy enough to change the form fields.
John