[Fedora-legal-list] Question about public domain file in dictd

Hi, I have been preparing a new update to dictd, and while doing it, I ran the licensecheck to double-check and cleanup the license tag. I found out that the licenses involved in the source code for the new 1.13.1 are more than originally specified in 1.12.x. There is a COPYING file with GPL-2.0-only, but the source code files have more. The final list is: GPL-2.0-only AND GPL-1.0-or-later AND GPL-3.0-or-later AND MIT AND GPL-2.0-or-later AND BSD-3-Clause There is one file in the source code that claims to be "public domain" [1]: This code was written by Colin Plumb in 1993, no copyright is claimed. This code is in the public domain; do with it what you wish This file is indeed code, so the allowed content exception for CC0-1.0 doesn't apply. The file is not written by the upstream maintainer but appears to be authored by someone else not in the maintainer list. I'm not sure how to proceed here. I could request the upstream developer to see if he can change the license but not sure will be able since it is not his. Would this be a valid case for Unlicense? [1] https://github.com/cheusov/dictd/blob/1.13.1/md5.c Thank you, Carlos R.F.