I have developed a program that I'd like to sell. It is available in two versions which are mutually exclusive. I'm now looking for a simple shopping cart solution that makes buying the program as easy as possible.
- have as few steps as possible, ideally work on a single page only.
- require a billing address and email address, nothing more (no customer login etc.)
- not require a shipping address since it will be available for download only.
- allow defining the number of licenses requested and calculate the total price
- support PayPal and prepayment
- work on a LAMP system
- be free (open source) or gratis (closed source) or cost less than 30 € (one time fee) (preference is in this order)
I think I read about such a single page solution in ~2012 in the German magazine for computer and technology (c't) but I can't find it any more. At that time I didn't know I'd need such a thing.