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 Ronald Bell:
Czech Daily Word provides you with a new Czech vocabulary word every day. Studying 1 word a day is a fun way to improve your vocabulary with little effort. Use Czech Daily Word every day and be introduced to 365 new words a year! Use the previous/next buttons to review words you've already learned or take a sneak peek at words that will be coming up soon! Czech Daily Word stores all data locally which means you don't need an active internet connection to use it! This is great for travelers who may have no/limited internet access. Study anywhere!