If you look at Dashboard as a way to turn quick-and-dirty web apps into real desktop applications, it suddenly looks very different from a straight Konfabulator rip-off. In fact, it really looks more like an interesting attack on XAML and Avalon, two of Microsoft’s additions to Longhorn. The underlying technology is different, but the fundamental goals are almost the same–allow people to develop both web and desktop applications using the same tools. The implementation differences reflect the basic difference between Apple and Microsoft’s approaches–XAML/Avalon is a ground-up replacement for HTML and the traditional Windows programming model, while Dashboard is really just a small tweak to something that already exists.
Update: As usual, John Gruber says it better then I can.