Last I recall you need to purchase developers license to use them in commercial 3D games
you don’t need it if you plan to use them as 2D objects
but that’s only for Daz figures, if you have content from other vendors or sites every item depends on the end user license agreement.
Correct. To re-use any mesh, you must purchase the appropriate game developer’s license. Note that not all content is available for such, but all DAZ originals and a lot of RawArt’s are if I recall correctly.