Dan,
It is possible to do recurring billing with paypal and activemerchant if you are have a Website Payments Pro Payflow Edition account w/ recurring billing enabled. This type of account isn't a standard offering on the paypal sites. I had to call a sales rep and specifically request this to get a special "token" I could use to apply. Activemerchant has built in support for doing recurring billing via Payflow using the Payflow gateway (which uses Paypal's XMLPay apis).
- Robin Curry