The extendible drawing editor Ipe is "free," this means that everyone is free to use it and free to redistribute it on certain conditions. Ipe is not in the public domain; it is copyrighted and there are restrictions on its distribution as follows:
Copyright © 1994 Otfried Schwarzkopf
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.