Thinking out loud here. Would it be technically possible for a computer program to use the data that describes a 3D mesh to generate a unique character sequence for that mesh? If so, could that be used as a basis for automatically checking whether a mesh is a copy of a previously uploaded mesh? If it is, but the author is different, then it could flag a warning of possible copyright infringement.
An e-mail could then be auto-sent to the person wanting to upload the copy, placing the burden on them to show proof that they have permission of the original creator, otherwise the copy does not go on the DLS.