License file is missing so please add one.
Also there's no license header on each file.

On CurseForge it says this addon is released under the GNU GENERAL PUBLIC LICENSE Version 3 from 29 June 2007.

According to the Internet Archive Wayback machine it has been like this at least since 2018 (when CurseForge re-designed their website and URL structure)

but... since there's no actual license file included, i think using this addon is a legal minefield.

This addon is fully open. Added the Unlicense to make that explicit.

Please add GPL-3.0 LICENSE to the repository and add -- SPDX-License-Identifier: GPL-3.0 to the top of each file to include the license information on each file.

You can't just add unlicense after the Addon was licensed under GPL-3.0 without the consent of all contributors.

I was interested in using part of this addon in one of my projects. Is there any intention in applying an open source license to this project?