The download button opens the iTunes App Store, where you
may continue the download process. You must have iTunes installed with an
active iTunes account in order to download and install the software. This
download may not be available in some countries.
From iSellMac:
Viewing your photos has never been the same! Try Photo Waterfall for mesmerizing visual photo entertainment.Import your favorite images to create amazing slideshows from: Photo Library Flickr FacebookThen view them in the Photo Waterfall! Unlimited photo slideshows!You will have to see it to believe how fun it is!Watch the Waterfall and tap on photos to view them fullscreen. Fast forward, rewind, and more!