Note that many websites have their own advertising, unrelated to adware.
From their website:
"ScreenScenes screensavers are provided free, because they are supported by advertising from the GAIN Network, which helps keep many popular software applications free in exchange for delivering advertising. As you surf the Web, you will occasionally see GAIN branded ads (pop-ups and others) selected based on your online activities. These ads are displayed by GAIN AdServer Software - not by any Web site."
These screen savers can be bought or downloaded for "free". The free downloads are ad-supported.