PS documentation file, no sources, author died
I have filed an ITP for octave-quartenion , a package from the
Octave-Forge Project . Its latest released tarball  contains a
documentation file doc/quartenion  in PostScript format for which no
source is available. There is also no Copyright notice in the file
itself, and there are no licensing conditions neither, although the
DESCRIPTION file  claims that the whole package is distributed under
the GNU GPL v3+. I think this violates the DFSG.
I would really like to distribute the documentation file but the upstream
author died recently  and the chances are small that the sources can
be found. Is there any rule that applies to this case, I mean, when an
A simple solution would be to strip the PS file from the tarball and,
eventually, create an octave-quartenion-nonfree package containing it.
Otherwise, we could generate a LaTeX file that reproduces that PS file.
If we do that, what should be the Copyright notice and the licence