Is the source for the guide available anywhere? I like the ideas in this a lot, but I think that I would need to play around with a concrete project built in it in order to really grok the practical implications.

The handbook seems to be here: https://github.com/gocircuit/escher/tree/master/src/handbook

Yes, the handbook is a complete Escher application. It simply creates a static file hierarchy while patching snippets of things together. Escher is experimental and I am iterating on other variations too. This one however is stable and complete and people are welcome to play with it.

The source is also on GitHub: https://github.com/gocircuit/escher/

Beautiful. Would it be feasible, suitable reasonable and practical to build ternary "circuits" in escher? Emphasis on practical

Escher can have circuits with any number of communication "valves", so ternary is ok.