"Traveling buss" is my favorite. Saves money on wire, confuses amateurs. I would be impressed by the building inspector who caught it.
This is a "California three-way" it doesn't say anything about this method being illegal in my book.
A better way is to actually use 2 spdt knife switches, a battery, and a light. Seeing how the circuit works physically goes a long way for those who have trouble understanding the concept.The best way to understand how to wire 3-way and 4-way switches is to get one of each and take a continuity tester to them.
So the California method is illegal? and it's the second picture I put up not the first? Is the second picture I posted similar to yours just layed out differently?