I had this same issue and the reason why it multiplies is because it's in a Content Editor WebPart (CEWP) as a <Script> when it should be Linked to a document in a library. Basically, copy the <Script> into a Notepad document then save it as Widget.htm on your desktop. Then create a New Document Library called Widgets (sounds good to me!), then add the Widget.htm file to the library. Click in the document and you will see the widget render as expected. Then the copy the URL from the address bar. Add a new CEWP to your web page and then paste the URL into the link section! BTW, I would not include http://mysite in the link, just use everything else it.

Now your widget is safely rendered and it will NOT multiply like magic bunnies.

Hope this helps someone out there! Oh BTW, this issue arrived to me after I migrated a 2007 to 2010 site.