The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From Kaz Agency:
Build and Share Holiday Cards by Email, Facebook and TwitterUse photos from your Camera, your Photo Album, or even your Facebook account to create a memorable Holiday Greeting for your family and friendsThis is not just another simple card maker with a few templates, this applications allows you to have tons of fun options with your design. The Build-a-Card application is based on our powerful "Picturizr" (tm) platform. The platform gives you the power to edit and personalize your Holiday Card with photos and various Christmas and Holiday themed overlays. You can pinch to zoom photos as well as position and rotate photos and overlays with your fingers. It is not too late to get out your Holiday Cards!Have a Happy Holiday!