DAZ (or Zygote, as they were known back then) made the Poser 4 figures. So if they did any copying, they were copying their own work.

As for D|S...they were afraid Curious Labs was going to go belly-up. They didn't want to be dependent on a program that might not survive, so they started making their own. Curious Labs been bought by e-Frontier, and is no longer in danger, but DAZ had no way of knowing that would happen.