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PyQwt License

PyQwt is released under the terms of the GNU General Public License with exceptions for use with the non-free versions Qt and PyQt.

Version 3, March 2006

PyQwt 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.

PyQwt 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 PyQwt; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

In addition, as a special exception, Gerard Vermeulen gives permission to link PyQwt dynamically with non-free versions of Qt and PyQt, and to distribute PyQwt in this form, provided that equally powerful versions of Qt and PyQt have been released under the terms of the GNU General Public License.

If PyQwt is dynamically linked with non-free versions of Qt and PyQt, PyQwt becomes a free plug-in for a non-free program.

Why a special license?

The GPL license covering PyQt and therefore Qt does not allow to release PyQwt under a lesser free license, such as the LGPL. The PyQwt license does not preclude the use of PyQwt in projects containing proprietary code.

The exception in the license is inspired by the GNU GPL FAQ.

Can I use the GPL for a plug-in for a non-free program?

If the program uses fork and exec to invoke plug-ins, then the plug-ins are separate programs, so the license for the main program makes no requirements for them. So you can use the GPL for a plug-in, and there are no special requirements.

If the program dynamically links plug-ins, and they make function calls to each other and share data structures, we believe they form a single program, so plug-ins must be treated as extensions to the main program. This means that linking the GPL-covered plug-in with the main program would violate the GPL. However, you can resolve that legal problem by adding an exception to your program's license which gives permission to link it with the non-free main program.

For more details, see the question above that starts with, "I am writing free software that uses a non-free library."

Application deployment

Distribution of a non-GPL-ed application containing a statically linked PyQwt module is a violation of the GPL. The licensing scheme for Qt and PyQt forbids me to release PyQwt under a license allowing static linking to proprietary applications.

Help to stop software patents

Free software and small and/or medium sized software companies are threatened by patents on algorithms and business methods.

  1. Read this excellent explanation of the devastating effects of software patents on software (users!) and software development (developers!)
  2. Read how the European Commission and the patent lobby are still trying to introduce software patents
  3. Support the Patent Busting Project of the Electronic Frontier Foundation in the USA