Amazon has discontinued the payment service we were using. We're looking into another alternative to PayPal. In the mean time, consider a prepaid debit card and a disposable email if you don't want to use a PayPal account and can't wait. The PayPal email doesn't have to match your SD email.

Update 2015-07-08
Sorry for the delay, but it looks like to use the new libraries we need to update a lot of back-end software and deal with required code changes. Progress is being made.