The piece images are taken from
They were created by Wikipedia users Inductiveload
and Hari Seldon (thank you).
The images are, as far as this is possible, in the public domain (see
was taken from
It was created by Sam Herbert (thank you).
It is "for everyone".
I assume this means: for everyone, for every purpose.
When in doubt, ask him.
The rest was created by Florian Spitzer. Copyright Florian Spitzer 2016.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.