the tarball doesn't include any information about the licensing of
the media files. Can they be licensed with GPL3 too?
Yes. They are effectively their own sources.
I guess the tarball should include a text file to indicate what license
covers the media files, am I right?
Yes.
https://savannah.gnu.org/task/?12939
Presumably the author intends more than just "free as in beer" :).
Thanks as ever, Joan.
karl
