Explaining the change, AT&T wrote that the sentence was added to assure licensees that the company would claim no ownership in the software that they developed--only the portion of the software developed by AT&T.
SCO conveniently overlooked this change when it decided to sue IBM. As AT&T's successor in interest, SCO is legally bound to honor the contract and publicly stated interpretation of AT&T's terms. That's why I think SCO's major claim against IBM and Linux will fail. The remaining copyright infringement claim is that Linux makes use of the Unix API (application program interface), and that copies of several header files defining that API were included in Linux.