GNU General Public License

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The GNU General Public License (short GNU GPL or GPL) is a collection of copyleft license published by the Free Software Foundation (FSF) and written by Richard Stallman.

This License is also part of the GNU project

Copyleft

A copyleft license requires that any modifications or extensions to a program licensed under a copyleft license must also be licensed under the same (or a compatible) license.

"or-later" clause

All GNU GPL licenses may contain an optional clause, an “or-later” clause (sometimes referred to as a “lifeboat clause”). This clause allows all later versions to be used. Programs without this clause are referred to as “only.”

for example

• GNU GPLv2-or-later can also be licensed under GNU GPLv3-or-later without any problem
• GNU GPLv2-only can only be licensed under the GNU GPLv2

The same applies to the GNU AGPL and LGPL licenses.

The FSF recommends using the “or-later” clause, as it is compatible with future versions of the GNU GPL, since GNU GPLv2 and v3 are not compatible and therefore a program licensed only under GNU GPLv2 cannot be mixed with a GNU GPLv3 program.

Licenses

There are three versions of the GNU GPL, with version 3 being the most recent version for all of them.

1. GNU General Public License (GPL) – The standard strong copyleft license used for most programs.
2. GNU Lesser General Public License (LGPL) – A weak copyleft license mainly used for libraries.
3. GNU Affero General Public License (AGPL) – Similar to the GPL, but also covers use over a network.

GNU General Public License (GPL)

This license is used for regular programs such as the Linux kernel, which uses GNU GPLv2 only. The latest version is the GNU General Public License Version 3 (GNU GPLv3), which was released in June 2007 and can be found here.

If part of a program (e.g., a library) uses this license, the entire program must be licensed under the GNU GPL. If this is not desired, the GNU LGPL or another license should be used.

GNU Lesser General Public License (LGPL)

The GNU LGPL (formerly known as the Library General Public License) was created at the same time as the GNU GPLv2 and was also published in June 2007, but the first version was called GNU LGPLv2 to match the GNU GPLv2. This license was created because the GNU GPL was too restrictive, especially for libraries.

If a program uses a library licensed under the GNU LGPL, only the modification of that library must be published. This allows a library to be used in Proprietary software

The latest version is version 3, which was published in June 2007 and can be found here

GNU Affero General Public License (AGPL)

The GNU AGPL was created to close a loophole when modified software licensed under the GNU GPL was run on a server the source code dont need to be published because of that the AGPL was created to fix this loophole

The latest version is version 3, which was published in June 2007 and can be found here