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# What Is Copyleft?

The simplest way to make a program free is to put it in the public domain, uncopyrighted. But this allows anyone to copyright and restrict its use against the author's wishes, thus denying others the right to access and freely redistribute it. This completely perverts the original intent.

To prevent this, we copyright our software in a novel manner. Typical software companies use copyrights to take away your freedoms. We use the copyleft to preserve them. It is a legal instrument that requires those who pass on the program to include the rights to further redistribute it, and to see and change the code; the code and rights become legally inseparable.

The copyleft used by the GNU Project is made from a combination of a regular copyright notice and the GNU General Public License (GPL). The GPL is a copying license which basically says that you have the freedoms discussed above. An alternate form, the GNU Library General Public License (LGPL), applies to certain GNU Libraries. This license permits linking the libraries into proprietary executables under certain conditions. The appropriate license is included in all GNU source code distributions and in many of our manuals. We will also send you a printed copy upon request.

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