the archive also contains the following statement:
»
Copyright (C) 2004 Gunter Gerhardt (http://www.xskat.de)
This cardset is dual-licensed
under the terms of the GNU General Public License
as published by the Free Software Foundation;
either version 2 of the License,
or (at your option) any later version.
or
under the terms of the Creative Commons public license
Attribution-ShareAlike 2.0 (CC-BY-SA 2.0),
or (at your option) any later version.
«
for my derived work I choose the CC:BY-SA and prefer 3.0+
to share – to copy, distribute and transmit the work
to remix – to adapt the work
Under the following conditions:
attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.