Modding Haven:Copyrights
In accordance with US Copyright laws, all video game modifications are considered the property of the original game developers. Mods are edits of existing assets or designed to replace existing assets and thus have similar file information as the original asset. These are not considered derivative works and thus are still subject to the copyright of the original creator. See the following links for more information:
Fair Use (FAQ) | U.S. Copyright Office
Circular 14, Copyright Registration for Derivative Works and Compilations