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 Ram Nelakantan:
This is an application very well suited for professionals and individuals on the move. Have you always wondered what might the international calling code be for a particular country? It is always cumbersome to look it up on the telephone directory or the internet. But now, you can have the country codes for all the countries right on your phone - which is the best place to store the codes anyway! This all new application provides a cool search function as well so that you don't need to scroll through pages of text just to find the code for a particular country. You can search by country code as well and the application will provide you the country. Now you will never have to search for that evasive country code anywhere else other than your phone!