The license is not specifically stated, and so defaults to "All Rights Reserved". This means developers looking to fork this mod in the future if it's ever abandoned would be unable to do so. Addons would also fall under violation. I'm not sure if a GPLv3-compatible license would work for this mod, but it would be preferable. A mod I've come to love, BetterPortals, is unable to add support because this mod lacks a license.