Then the author of that addon would be liable. Not blender.
Try it and see if it is blender or you as the addon creator that gets sued.
These AI models are closer to Google in that regard, yes, you can instruct them to generate a Mickey Mouse image, but you can instruct them to generate any kind of image, just like you can search for anything on Google, including Mickey Mouse. When using these models you are essentially performing a search in the model weights.
Google Image results have a note that says: “Images may be subject to copyright”.