5bx is a generic payment gateway sandbox. I originally developed it for my Web Development students who were often tasked in their capstone projects to integrate a payment gateway solution into their eCommerce sites. Doing so often posed a challenge, with many students reluctant to sign up for developer accounts at the major gateways. It is, essentially, a teaching tool...
I also developed 5bx for my own use, so I could "mock up" payment processing in my own projects, without going to the trouble of signing of for unique Payment Gateway developer accounts for each one