I see that it's licensed under the GPLv3, but where's the source?

EDIT: Maybe it's this one[1], but it's under a different license, AGPLv3. The repo also hasn't been updated since 2016, but the extension page says last update was in 2018. Are the changes and re-licensed source elsewhere?

[1] https://github.com/internetarchive/wayback-machine-firefox