Daz may rewrite their EULA in even more complex terms in an attempt to clarify this issue, but a simple rule of thumb is that a product is derivative if it has at least 5-10% shared content. In addition, if we buy a DAZ product, possession of that product can be used as circumstantial evidence, if we then try to sell any kind of similar product, so maybe that's what they're trying to say in a somewhat clumsy manner that's obviously causing alot of worry. Not exactly "anything you buy may be used as evidence against you in a court of law", but something like that.