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 KiDAkil Software:
Amazing Nature Wallpapers is a collection of 20 beautiful nature photo wallpapers for your iPhone. The photos were taken by professional photographer Patrick Lynch. If there is a particular photo that really moves you, and you are inspired to share it, simply email the wallpaper to a friend. You can also save the wallpapers to your photo library. * 20 Stunning Nature Wallpapers * Easy navigation - Just swipe left or right to move between wallpapers * Slider control allows you to instantly move to any wallpaper quickly * Menu button toggles the menu on/off so that the menu only appears when you need it * Save wallpaper quotes to your photo library * Share wallpaper quotes with your friends and family