Payment Gateway
A payment gateway is an intregal part of an eCommerce solution. Whether a website has a fully-fledged eCommerce capability or one-off payments or donations are required to be processed, a gateway is needed.
A Gateway is a means that your website can interact with a banking system. The Gateway provides a method to facilitate Electronic Funds Transfer (EFT). The Gateway can be an intregal part of a "Shopping Cart" or mearly a button or form to allow a visitor to make a single or recurring payment.
Irrespectively on what "platform" is decided on for the "Friends" a Payment Gateway has to be part of any eCommerce activity.
Decision
The intergation of Payment Gateway for my websites is likely to use the technologies of Stripe.
The decision was based on that Stripe is used by Thyngs for their offerings for charities such as Macmillan and also by Wordpress.com (as a free payment scheme).
on-line payment on Wordpress
This involves adding payment buttons and connecting to stripe.