ah you right, Jeff. I was confusing the charms with applications extensions like file picker and search provider.
So there is no extension mechanism in metro style apps that would allow 3rd party to extend our metro app via the market place?
What about if we implement extensions ourself in our metro app. Could we download (trusted) code inside our app, store it on the users computer and execute it inside our metro app?
We could download the available extensions (js, css, html) from our own website when the metro app is running, and store it in a place our metro app has access to (user folder?).