I think that the reason for the account limitation is because the buyer is claiming that you are preaching to people to scam Paypal in order to make money. While that does not appear to be the case by the instructions as I see what little I see, the Paypal reviewer is not taking the time to be so understanding...they see "involve scamming Paypal" and they want to burn you. You need to read up on disputing account limitations, as it is possible to get them removed (your account reinstated to full status) but it is probably going to take you reaching someone @ Paypal who has a "brain" and also has "authority" to actually make a decision that involves using that brain. Not always so easily found at Paypal.
I know what type of program you are talking about, as I bought an eBook by doing something similar. The ebook seller gave me 2 options to pay: Paypal, or sign up for something...there were multiple choices of what to sign up for. If I signed up for a program, I got the ebook free, if not, I had to pay. Bottom line is, he more than likely got paid even more for my trial signup than if I had paid cash via Paypal.
However, not everyone at Paypal will get that kind of marketing. And the person who bought from you obviously does not! Their automatic "scam" label on the product is actually most likely what is causing Paypal's reaction of account limitation. This offer has to do with companies understanding the lifetime value of the average customer. Therefore they offer something that seems like they lose money up front in order to get the customer in the door. In the long run the averages make them a hefty profit so they don't mind the losses on some orders, the averages more than make up for it. It's like the grocery stores that offer items for 9 cents because of some special promotion when that item usually cost a dollar when the special is over. They know once they get their hooks into you (get you in the door) you'll spend more than enough to make up for the small loss they took on that 9 cent item. Okay, maybe YOU might only buy the 9 cent item and nothing more, but how many other people also came in intending to only spend 9 cents and walked out with a shopping cart full of stuff, dropping $100+ on stuff they remembered they needed "while here".