Lucki [1] filed a orphan request for unknown-horizons [2]:

I would like to adopt this package as it seems to be abandoned by it's current maintainer. I can't find any activity of ChrisOelmueller in the last half year. This package got an update two weeks ago, I flagged the package and provided an updated PKGBUILD right after that flagging with a comment. Both actions should have sent him an email so I think he's just not interested in maintaining this anymore.

[1] https://aur.archlinux.org/account/Lucki/ [2] https://aur.archlinux.org/pkgbase/unknown-horizons/