Or they could integrate a way to find the produced output back in the corpus if it's sufficiently close and provide a reference/attribution. Basically whatever tool a copyright lawyer would use to track down original work.
And that's just the engineering solution. The AI researcher solution would be to extend AI learning algorithms to attach attribution metadata to the learned data so that the output could already come annotated with information about the source.
But the latter is much harder to do, so maybe the engineering solution would suffice.