Barbarians use the same tech-stealing mechanics as city-states do.
The only problem is, in his mod, he has over 100 techs, and the prereqs are all in a straight line. Usually the result of this is that not enough civilizations research the tech at the same time, so barbarians can't steal it, and they don't spawn.
In my Ancient World, the tech tree is more like vanilla, so barbarians will spawn at the intended times because the techs branch out so that most civs reach the same tech at the same time. When everyone gets Quadriremes in my mod, the Barbarians will get Pirate Ships, and when everyone gets Iron Working, Barbarians will get Swordsmen, etc.
Also, please note that don't give Barbarians resource requirements, or they won't spawn their unit.