Brad Neuberg left a comment on where to find the proxy...or rather, that left me an email address so I could email him that there was no download link :P I've got it now, so now I can transclude the introduction from the purple-include page here directly (note: probably Firefox only at this point -- you should some purple text below after this rolling symbol: ):
And that was just one more line in the Drupal module to set the meta tag:
drupal_set_html_head('<meta name="purple_proxy_path" content="/' . $path . '/purple-proxy.php" />');
Now I just have to hope that bad, terrible things won't happen from this proxy.