Greetings debian-legal! I understand Debian includes the package libbsd in Debian main. This package includes a man page with the following license (see https://git.hadrons.org/cgit/debian/pkgs/libbsd.git/tree/debian/copyright#n214)
License: BSD-5-clause-Peter-Wemm Redistribution and use in source and binary forms, with or without modification, is permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice immediately at the beginning of the file, without modification, this list of conditions, and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 3. This work was done expressly for inclusion into FreeBSD. Other use is permitted provided this notation is included. 4. Absolutely no warranty of function or purpose is made by the author Peter Wemm. 5. Modifications may be freely made to this file providing the above conditions are met. I'm curious if there are opinions on why "must retain the above copyright notice immediately at the beginning of the file" is consistent with the DFSG. This is one of a variety of 1990s FreeBSD 3-clause BSD variants with such a feature. Richard