Keep in mind what is the tool and what is the creation. Poser (or DAZ) created the P4 Male and P4 Female to work with Poser. They are the copyright of the creator (Poser). If you use some other 3d modeling tool to completly create another figure (the Creature from the Back of My Mind, sort of speek) then even though that figure works in Poser, it's your copyright, and your creation and can be sold, unlike the P4 models. Like Alleycat said, there's a lot of tools that go into making a house, but it doesn't mean the house belongs to the guy who made the hammer.