So I'm working on a mod that will contain references to different franchises from different copyright holders, and I'm wondering if I have to obtain permission from the various owners to use their content. This probably seems like a silly question, but hear me out first. I know there are rules requiring that I obtain permission, but there are music mod packs on steam workshop that contain music from a dozen different copyright holders, and I seriously doubt that the authors of such mods were able to get in contact with, and obtain permission from the various copyright holders. Already asked on reddit and got great responses, though I would also like the opinion of the paradox forums.