Google would lose if they would continue hammering the interop point and the justices would dig deeper. Google only copied a selective set of Oracle's Java libraries. If they were about interop, they would have copied all of them. So no, Google didn't copy the libraries because of interoperability reasons. Google copied them so they would get access to the large developer community and ride the coattails of the successful investments into the Java platform that Oracle made. As one of the justices said, it's a one-way interoperability.