The project can be downloaded and run locally (it is a static client side website, no server) and the proof generation and verification can be run offline, with

The project can be downloaded and run locally (it is a static client side website, no server) and the proof generation and verification can be run offline, without the coordinates ever being sent over the network. Only the proof file needs to be sent between the two parties. I suppose the system itself acts as a “third party” but at no stage does it require you to share the coordinates with one another, hence zero knowledge. :) Does that make sense?