Here's my use case: I have a Paypal "Buy now" button that I have created using Paypal's Website Payments Standards utility. This provides an Instant Payment Notification when a user successfully makes a purchase.
What I would like to do is automatically give a user a role upon a successful purchase. I installed the lm_paypal module, but it is a full-featured subscription solution which I don't need; all I want to do is give users a specific role. (It's impossible to configure lm_paypal to simply give a user a role; it wants to turn the role into a subscription, but my use case is not a subscription.)
At worst, I can just add the role to user accounts manually when I receive payment, but I'd like to find a way to do it automatically.