Unlike most of the "free" web-based services this autoresponder/newsletter software is not "adware" of any sort. There are no banners and no "sponsor" ads added to emails sent by the software.
On the other hand, you can add as many advertisements as you like. In fact, this is probably precisely why you are interested in our autoresponder/newsletter software in the first place; because you want your customers to receive marketing information about your products. They are your customers after all!