you can set a php file in your domain with the following code :
$rss = file_get_contents("http://something.com/rss");
and then query this file via AJAX
but you might have some trouble parsing it since for now the XML object doesn't seem to like namespaces.
and of course it won't work for preview.
Thanks for your help. I would like to ask you something, did you try to Load URL from Image for a sprite, in that case, you get a Google logo image URL? It didn't work for me.