Vaadin & XSS WEB Widgets that communicate with a 3rd server

I am trying to build a web widget that could be embedded in any web page.
The web widget would then get data and communicate with a thrid party server.
I do not want the Javascript on the client to go to the server the Javascript got downloaded from and proxy all comm to the 3rd part server I want the javascript to talk directly to the 3rd party server.

Most Web widgets are built that way, (for example Google maps, YT mebeddable player etc), I know most of the stuff due to security restrictions is done with JSON…
any neat way to go about with Vaadin without doing it all the old fashioned way?

What I am talking is building web widgets …not to be confused with vaadin toolkit widgets…word widgets is used all other but I specifically refer to WEB WIDGETS.
Say like the ones on WidgetBox.com.

Simply out in other words…how to build a YT widget with vaadin or any form that people can embed into their web pages that allows submitting to MY SERVER.

This is basically all XSS and there are also the cross domain issues with ajax to be addressed. if I could use Vaadin…this would make it all much neater…problem is
I am not too sure if the Vaadin model can support it all OUT OF THE BOX.