Shopify/active_merchant — pull request #215 by Alamoz (2011-10-28 03:14:33+00:00)
Title: Give express checkout the ability to checkout customers in guest account mode.

Add ability to checkout users as guests, which means they don't need to create or use a PayPal account to pay, they can pay with just their credit card. When calling the setup_purchase or purchase methods on the express gateway object, invoke this as:

@response = EXPRESS_GATEWAY.setup_purchase(
amountamount,
:allow_guest_checkout => true,
...etc.
)