Ok, modifying the config.js did the trick, now I can Video- and Voice- chat with clients located at the same network. GREAT 
(Though I had to do some minor changes to the config you've posted, I pointed them out in the comments of your blogpost)
Though it's not possible to connect users from outside lan.
They can access the website, can use the webchat but the video screen stay black.
( i think there was also no audio, but I'm not sure on this)
I was sitting at my firewall watching logs and there were "obscure" packets like the openfire server was trying to send packets to the internal ip address(192.168.x.x) of the user that tried to connect externally.
(udp packets only)