Questions regarding public-domain (well, again)

[Lev Lamberov <dogsleg@debian.org>]

Hi,

i've already wrote that i work on a migration of swi-prolog package to
machine-readable d/copyright. I have some more questions and need your
advises. There are several files which contain a copyright notice
stating that these files are in public domain. Well, I understand the
difficulty and problems regarding public domain, and read some previous
discussions on debian-legal@l.d.o. These copyright notices are (for
example):

This code is in the public domain and has no copyright.

Or:

The libtai code is in the public domain, so you can use it in your own
programs.

Others contain just something like as follows (from the package
documentation):

This example code is in the public domain.

I believe that for a great bulk of these public domain files I can get a
special notice or explanation (if it is necessary), since the author of
these files is one of the authors and the current maintainer of
SWI-Prolog itself.

So, the main question is what to do with these files, and if it is OK to
keep them (maybe asking upstream for some clarification of their
copyright statements), then how to corretly fill the d/copyright file? I
mean that 7.1.1 of Machine-readable debian/copyright file (version 1.0)
is not clear for me.

Currently I have something like as follows:

Files: packages/clib/demo/*
       packages/http/examples/demo_daemon.pl
       packages/xpce/man/course/bib.pl
       packages/xpce/man/course/fam.pl
       packages/xpce/man/course/ftp.pl
       packages/xpce/man/course/learner.pl
       packages/xpce/man/course/lib/prompt.pl
       packages/xpce/man/userguide/examples/graphedit.pl
       packages/xpce/man/info/dialog.pl
       packages/xpce/man/info/which.pl
       packages/xpce/man/info/window.pl
       packages/xpce/src/gnu/getdate.c
       packages/cpp/likes.cpp
       packages/cpp/test.cpp
       packages/cpp/test.pl
       src/libtai/*
       src/tools/functions.pm
       src/tools/update-deps
       scripts/swipl-bt
       customize/dotxpcerc
       library/dialect/bim.pl
License: public-domain

As I understand I should put some explanations right after 'License:
public-domain', right? And what to do with lintian warnings:

W: swi-prolog source: missing-field-in-dep5-copyright copyright (paragraph at line 244)
W: swi-prolog source: missing-license-paragraph-in-dep5-copyright public-domain (paragraph at line 244)

Should I override them?

With regards,
Lev Lamberov