It is built with GWT. If you show the page source You'll find gwt:property
and __gwt_historyFrame also there is the recognizable <script type="text/javascript" language="javascript" src="/forum/9DFBD72A740A67486E2A6B81D6A00C25.cache.js">which points to the GWT javascript. -- http://groups.google.com/group/Google-Web-Toolkit-Contributors
