"TrialPay is a method that allows you as a customer interested in product X to get it for free by subscribing or (optionally) purchasing a product from one of their sponsors. Practical example: You can get a free WinRar license (with the same rights as a user that buys directly from winrar) by signing up for a 30-day trial on Stamps.com
Of course that these offers from advertisers vary a lot depending on your country (there can be more than 100 offers for people in USA, whereas 1-2 offers for people in Romania).
Is TrialPay a scam? Far from it, and the fact that they are backed up by investors behind Skype, Google and Akamai (info here) looks promising for the growth of this system. Also, I was able to find over 130 trial pay offers, including products like Winrar, Winzip, Zonealarm and if these large companies trust TrialPay enough to associate their names with it, I would say you can rest assure it's not a scam.
Here is an image from their site that shows how this system works:
As you can see, you click on the Checkout button for the product that you're interested in obtaining the free license for, you browse then through the offers from 3rd party advertisers like Vonage, eBay, Discover Card, Lancome(and search carefully, because there are some offers that only require you to subscribe without paying to some service), you complete the offer as described in there and voila, your license is delivered.
Now, where's that list of trial pay offers I kept talking about? Well, it took a while to get it together (given that they don't have that on the Trialpay website), but here are 132 trialpay product offers (first 15 are more interesting, given those are more popular products - each product offer has in paranthesis a short description about the program and also the price that it's normally sold for, that you don't have to pay)."
MORE: [Only registered and activated users can see links. ]