Avaya vmail portal via AAM - can I customize or alter the home page?

hi all, happy post Thanksgiving. does anyone know how Avaya built the AAM voice portal? I'm referring to the internal website that users access when they want to listen to messages and or delete them. at my current org we have a secure website and it's just the where xxxx is our internal company domain. I ask because when the page opens you have 2 options, enter a Mailbox and enter a Password. I want to see if we can add more options or buttons to this page ourselves but don't know anything about how it's built, what is the engine behind it, etc.
I know we may have to go to APS and pay for any customization, but would love to have some background before I go down that road.