This is an important distinction to say P2P webrtc is limiting. WebRTC is just a collection of protocols, codecs, etc. There isn't anything stopping you from using WebRTC as a user endpoint that talks to a centralized server. I used google's java wrappers included in their WebRTC implementation to get a toy server working.
I played with the idea of relaying a stream across multiple nodes and it works. What I was doing was kinda silly I guess since it is way to cpu intensive to open so many media streams, but the general idea works. I guess it would be better to have the user endpoint talk to the server through a mediastream and then transcode the data for consumption like other systems do it.
I'm sure it's amateur compared to a project like Jitsi, but was still interesting to get working. I haven't played with it in several months but the code was here: https://github.com/jgrowl/livehq
The actual server code is here: https://github.com/jgrowl/livehq/tree/master/media/src/main/...