Photopass itself, just getting the card and being able to view the pictures on the web, is free. You can look at the shots, do some editing to the pictures, and share them with friends. However you cannot save the pictures or print them and they are available online for a limited time (90 days I think is the limitation). Whether you buy the pictures or not, at the end of that time the pictures are deleted from their server.
It's all fair really, my only complaint - And not a huge one at that - Is that I think if you order the prints, you should be able to download the photos as well (and save time then with scanning the pictures into the computer).