gistfile1.txt

server.serializeClient(function(clientString, done) {
  // @TODO for some reason clientJSON is not valid JSON
  console.log('clientString = ' + clientString);
  var client = JSON.parse(clientString);
  console.log('_id = ' + client._id);
  console.log('name = ' + client.name);
  console.log('secret = ' + client.secret);
  done(null, client._id);
});

Output:
clientString = [{"name":"CollabClient","secret":"CollabClientSecret","clientID":"CollabClientID","redirectURI":"/auth/callback","_id":"50b2ad73affd031c1d000001","__v":0}]
_id = undefined
name = undefined
secret = undefined