We think that a good license for free software should give both users and developers maximum freedom, while being short and easy to understand. Most of our software is thus licensed under the MIT/X11-License as below:
Copyright (c) <year> <copyright holders>
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
Due to external constraints there are exceptions from this policy. Please see the LICENSE file of each source package to find out the particular license in effect for a project.
We do not consider the GNU General Public License (GPL) to be compliant with our goals, as it is a long and complicated legal document, which imposes a lot of restrictions on both the users and the developers rights. It also increases the risk of license incompatibilities when merging projects. According to the GPL FAQ, the question whether such license incompatibilities take effect, is dependent on the “intimacy” of the communication between two pieces of software. For the definition of “intimate communication”, the Free Software Foundation refers to judges, which should finally decide how to interpret the GPL and applicable laws. We do not want to let judges, lawyers or prosecutors decide, what is allowed and what is not allowed to do with our software. We just want to allow as much as possible.
Using a liberal license like the MIT-License releases developers and users from many legal constraints. It also encourages companies to use and to contribute to the software.