Here, they said that the development was slowed down because of disagreements, and a sizable part of the development team announced their fork:
Again, benefit of hindsight, but 0AD's releases have always been pretty slow, and it doesn't look like this was really out of the ordinary?
It's hard to have good faith on the part of the forkers when it sounds like they took issue with how closed/"iron fisted" the development of 0AD was, and then ... made a fully private fork with 3 people?