@minimoysmagician you can't, yet. Although they did promise to open-source it some time ago. You can audit *parts* of the stack- #Pears & #Holepunch, specifically.
I suppose in that regard it is as auditable as Signal, who, as we know, have been pretty unresponsive when it comes to making up-to-date source for their server code available 馃し馃徎