The fact that you use the word "gadget" to describe your app makes me think you're using Google Sites, in which case I don't think you'll be able to do anything. If that's not the case, though, you can certainly include libraries which are not hosted on Google's CDN simply by pointing a script tag appropriately. In the case of Raphael, this means that you'll have to download the source, save it to your server somewhere, and then include something like this on your page:
<script type="text/javascript" src="/path/to/raphael.js"></script>
Then you should be able to use it. Again, IF you're NOT using Google Sites. If you're using Google Sites, I don't know that you'll ever find a solution.
jg