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.
The Ticketbud barcode scanner uses the camera on your phone to read barcodes and validate the Ticketbud tickets you have sold or given away. You will need an account on http://ticketbud.com to use this application.