Cartes du Ciel is free software released under the terms of the
GNU General Public License
Cartes du Ciel software, Copyright © 2006 Patrick Chevalley
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 2 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.
You should have received a copy of the GNU General Public License along with this program; if not, see http://www.gnu.org/licenses/
The different catalog data are generally public domain but an acknowledgment to the original catalog author is require if you use this data for your research.
You are free to use any chart or print produced by the program for any use, commercial or not (blog, web publication, printed book,…). You can mention Skychart and link to the main page, but this is not required.