The models created by Metahuman are under license, but if you were to copy the mesh, how it looks, then delete the original metahuman, then use other 3rd part tools to add hair, clothes, rig, bones, etc. That copy is not under the license, because it was not created by metahuman software.
They cannot copyright 3D looks unless it is an Intellectual property like Iron man TM. Correct me if I am wrong.