Hi Daffadile,
Thanks for your interest in Envrin Group. Let's see if I can answer your questions:
But why do people have to register before they can buy?
It only requires an e-mail address and desired password. It's simply to create your a client account, so you can manage your license, submit support tickets, etc. We need to know who our clients are, because almost guaranteed you'll need some type of support.
How can there be no fees? How would you make money then ?
Let me clarify. By "no fees" I mean Envrin Group doesn't charge any usage fees, such as how folks like BitPay charge fees to use their service. However, you as administrator can define fees for sending, buying and selling coins, which are charged to your users.
How could this be used to add credit to a users account with a website ?
Not sure if I quite understand the question. The software does come with a fully featured transaction system where you can easily add funds into a user's account if desired.
Hope that helps, and let me know if you have any further questions.