Tharbad [1] filed a deletion request for virtualbox-ck-modules [2]: No longer needed. Replaced by virtualbox-dkms. I've waited to see if anyone needs it for the last year. No requests. Therefore it's safe to delete.
[1] https://aur.archlinux.org/account/Tharbad/ [2] https://aur.archlinux.org/pkgbase/virtualbox-ck-modules/
