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 Networking 2.0:
This app allows you to browse street level map of Dallas when you are traveling. You don't need to have internet connection for this to work as the map is stored on your iPhone or iPod Touch. Ideal for saving roaming charges or having to find the local wifi to access the built-in map application.You can pinch to zoom in and out of the map just like you can with the built-in map application.We are currently building and field testing support for GPS and this will be released as a free update soon. Stay tuned.The source of the map is from Open Street Map, http://openstreetmap.com/ under Creative Commons Attribution-ShareAlike 2.0 license.Follow us on Twitter.http://twitter.com/ondemandworld