I've written a bit of software that I'd like to share with others (a Mac Dashboard widget, specifically), but I'd also like to be compensated a bit for the time I spent on it. I've devised my own simple registration key algorithm, which takes a customer's email address and creates a 12-character alphanumeric key. The software itself is finished, demo limitations, key validation & all.
I just need to get the keys to customers. How do I simply alert a key generation script to automatically email a customer a key, upon notification that they paid my account? Can I use PayPal IPN & JavaScript?
The simplest solution will do - this is a five dollar widget. :)