Licensing question about data for KStars

Hi

In KStars, we've been using unreliable data for what we call 'deep-sky
objects' (galaxies, star clusters, nebulae etc) because of licensing
issues. I've been wanting to fix that.

I wrote a mail to the editor of a popular database of deep-sky objects
used by several software (many of them under GPL) about using it in
KStars and re-distributing it under GPL. This was required because the
documentation says that the "data is released for private use of
anyone who wishes to use this database."

I got a response saying: "I have no problem with you using the SAC
data for the Kstars program.  It was released with the rules that it
is not sold as a seperate item." There have been other instances where
the redistribution under GPL has been permitted (See
http://www.freelists.org/post/sac-board/Permission-Request,5 for
instance)

1. Is this permission sufficient, or is something more required to
   redistribute the data

2. Is it required that I assign the original author / editor of the
   original catalog as one of the copyright holders of the
   GPL-licensed catalog?

3. I also used the HyperLeda database, which is used primarily for
   research purposes. They expect an acknowledgement in the following
   manner:
   http://leda.univ-lyon1.fr/acknowledge.html
   However, they do not specify any licensing terms. Would it be
   appropriate to use their data in KStars?

Currently, my proposed copyright notice looks like this:
# NGC/IC catalog (c) 2003-2009 by
# Jason Harris <[email protected]>, Akarsh Simha <[email protected]>
#
# This catalog was constructed from:
# 1. Saguaro Astronomy Club Deep Sky Database version 8.0 [Data used with permission] <http://www.saguaroastro.org/content/downloads.htm>
# 2. Other Public Domain Sources
# 3. We acknowledge the use of HyperLeda database for NGC 6218 and NGC 6334 <http://leda.univ-lyon1.fr>
#
# This catalog is released under the GNU General Public License:
# http://www.gnu.org/licenses/gpl.html


TIA.

Regards
Akarsh
Maintainer, KStars.