PayPal is rolling out a flexible payments API called “Adaptive Payments”. Similar to Amazon’s Flexible Payments Service (FPS), the Adaptive Payments API handles payments between a sender of a payment and one or more receivers of the payment. Adaptive Payments allows almost the same functionality as FPS. The new API lets developers become a payment aggregator, which we are told is something against PayPal’s current Terms of Service.
More info: Adaptive Payments