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 © 1993–2016 Otfried Cheong
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.
As a special exception, you have permission to link Ipe with the CGAL library and distribute executables, as long as you follow the requirements of the Gnu General Public License in regard to all of the software in the executable aside from CGAL.
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.