Interesting note on Dave Hyatt's site about Dashboard and the version of Safari that will ship with Tiger (Hyatt is the lead developer on Safari):
[The Dashboard widgets] are Web pages, plain and simple (with extra features thrown in for added measure). Apple's own web site says "build your own widgets using the JavaScript language", but that's sort of misleading. The widgets are HTML+CSS+JS. They are not some JS-only thing.
So Dashboard is perhaps a bit more like IE4's Active Desktop than Konfabulator (Konfab is pissed at Apple for ripping them off).
His post also hints a couple of times to WebCore changes to faciliate Dashboard features and the RSS/Atom features in Safari: "each widget is just a web page, and so you have the full power of WebKit behind each one... CSS2, DOM2, JS, HTML, XMLHttpRequest, Flash, Quicktime, Java, etc." and "fixes to WebCore to support Safari RSS and Dashboard". This is really quite exciting. RSS/Atom parsing will be built right into the OS. With Webcore, Dashboard, and Apache on OS X, the lines are blurring between apps and Web apps. Nothing new (hello, push), but it's nice to see action in this area.