Apologies: the code for this example has been moved to here.
(Been meaning to update the article, but haven't had a chance...)
The apprtc.appspot example uses the Channel API on App Engine for signaling, but there are lots of other ways to do this. Signaling mechanisms are not defined by the WebRTC spec. (Note that signaling, which is accomplished via a signaling service, is the exchange of network and media metadata in order to set up a WebRTC 'call': the actual data is communicated directly between peers.)
We ran a codelab at Google I/O, which describes from start to finish how to build a video chat application that uses Socket.io on Node.js for signaling (it's very simple!) You might want to try that instead.