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 NKPM:
The Tickle Network - We are all happy people :-)Using the Tickle App you can tickle others.> Tickle your girlfriend when you're thinking about her.> Tickle friends when you're bored.> Tickle strangers to date them.> Tickle someone wherever he is.> Tickles are free!> Tickle is fun!> Tickle is without any obligation!> > > Finally: To tickle is just the begining!The Tickle iPhone Application gives access to the Tickle Network. Everyone in the Tickle Network can tickle each other by shaking the device. You'll be tickled by receiving a message (Push notification) about who tickled you. To use Tickle is free!To access the tickle network you simply sign up with a name and a picture. As this can be freely chosen you're free to join anonymously with a fantasy profile :-).