The Dashboard App, designed for use with Apple's new tablet, was made to offer you the experience of using Apple's OS X interface, found on Apple desktop machines and notebooks, on the iPad, which many had bashed for being too iPhone-like. Interesting idea, right? Apparently, Apple didn't think so.
It seems Apple felt the Dashboard app was "Contradicting iPad's User Experience" and they rejected the app altogether. Which makes little sense to us, because downloading this app is a decision left solely to the end user, who would be aware that it wasn't the original "experience" that the iPad offered because they downloaded it.
Regardless, it's now off the App Store, but you can still get your hands on it and download the source (if you're a developer) off of GitHub and put it on your iPad manually.
It's funny - for a company that appears to be all about fostering of innovation and creativity, they sure seem afraid of anyone applying it to their devices.