The signaling server for the Unity asset WebRtcVideoChat is now open source under the BCD license with its original typescript source code. You can find it on github under its new name awrtc_signaling.
The current master branch is already prepared for the next version V0.984 and contains several changes such as updated dependencies, stability improvements and support for heatbeat messages which will allow the client side to detect disconnects quicker. It is also backwards compatible to all earlier versions. An update to the new version is highly recommended.
Please feel free to contribute and report issues & suggestions to the github issue tracker.