This is a startup, the application is not open source but everything we use is. We are building on the Microsoft stack, which might make it uninteresting for most of the HN crowd. Our main framework components are Orleans, Nancy, SignalR, Knockout.js and Xamarin. I think one could get the same results using Akka, express, socket.io, flux and React (or Ionic with angular)
It'd be interesting to hear about the issues you've found around SignalR and offline mode, as we are building on very similar stack so far and your experience can help others who are using Orleans