Here\'s the goal:
Hand off a script tag that references a JavaScript file on a remote server. That JavaScript file should return HTML that will then be displayed on
You will need a server-side proxy for x-domain calls.
There are many implementations available online or you could probably whip one up in language of your choice to fit into your stack.
More info with graphics and a PHP proxy available here - http://developer.yahoo.com/javascript/howto-proxy.html