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.
So you and your friends want to play some volley ball. The hardest part is keeping score. Not any more. VBScore will keep track of the score with volley ball rules built in to the app. It also has a basic score keeping system where you just set the winning score and VBScore will notify you when you have a winner.