Posted 07 January 2012 - 04:03 PM
There is a way to do this by using your PayPal account.
First, you need a PayPal account. Now, when you get the, I think, widget for buying stuff with PayPal, you would also have the person enter their e-mail and other information. When the person buys the game, the e-mail would be sent with a code that will be used when you enter it into the game, which then the server will receive that code and see if it is correct, and if it is, then in the text file containing the information for the account there would be a value named 'registered' and that would then equal true, which then the server would allow you to do the things that only payed users would be able to do.
That is the way I would do it. If you want it so people don't steal that code, make it so that there is a text file that contains all the codes that are generated, which would be generated using a certain algorithm(such as the first letter would have to be a letter A-G, second letter H-P,ect.). From there, once a person buys a code, a random code is sent to that person, and when they enter it in, that code would then be deleted from the list and could not be used again, unless an administrator put that code back in.