Various Licenses and Comments about Them - GNU Project - Free Software Foundation (FSF)Various 
Licenses and Comments about Them
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Table of Contents
  Introduction 
  Software Licenses 
    GPL-Compatible Free Software Licenses 
    GPL-Incompatible, Free Software Licenses 
    Non-Free Software Licenses 
  Licenses For Documentation 
    Free Documentation Licenses 
    Non-Free Documentation Licenses 
  Licenses For Works Besides Software and Documentation 



Introduction
We classify a license according to certain key questions: 
  Whether it qualifies as a free software license. 
  Whether it is a copyleft license. 
  Whether it is compatible with the GNU GPL. (This means you can combine a 
  module which was released under that license with a GPL-covered module to make 
  one larger program.) 
  Whether it causes any particular practical problems. 
If you want help choosing a license, evaluating a license, or have any other 
questions about licenses, you can email us at <licensing@gnu.org>. 
By the way, if you believe you have found a violation of one of our copyleft 
licenses, please refer to our license violation page. 



Software Licenses
  GPL-Compatible Free Software Licenses 
  GPL-Incompatible, Free Software Licenses 
  Non-Free Software Licenses 



The following licenses do qualify as free software licenses, and are compatible 
with the GNU GPL: 
GPL-Compatible, Free Software Licenses
  The GNU General Public License, or GNU GPL for short. 
  This is a free software license, and a copyleft license. We recommend it for 
  most software packages. 
  The GNU Lesser General Public License, or GNU LGPL for short. 
  This is a free software license, but not a strong copyleft license, because it 
  permits linking with non-free modules. It is compatible with the GNU GPL. We 
  recommend it for special circumstances only. 
  Between version 2 and 2.1, the GNU LGPL was renamed from the GNU Library 
  General Public License to the GNU Lesser General Public License to better 
  reflect its actual purpose. Namely, it is not just for libraries, and the GNU 
  GPL is sometimes more appropriate for libraries. 
  The license of Guile. 
  This consists of the GNU GPL plus a special statement giving blanket 
  permission to link with non-free software. As a result, it is not a strong 
  copyleft, and it is compatible with the GNU GPL. We recommend it for special 
  circumstances only--much the same circumstances where you might consider using 
  the LGPL. 
  The license of the run-time units of the GNU Ada compiler. 
  This is much like that of Guile. 
  The X11 license. 
  This is a simple, permissive non-copyleft free software license, compatible 
  with the GNU GPL. XFree86 uses the same license. This is sometimes called the 
  "MIT" license, but that term is misleading since MIT has used many licenses 
  for software. 
  Expat license. 
  This is a simple, permissive non-copyleft free software license, compatible 
  with the GNU GPL. It is sometime ambiguously referred to as the MIT License. 
  Standard ML of New Jersey Copyright License. 
  This is a simple, permissive non-copyleft free software license, compatible 
  with the GNU GPL. 
  Public Domain. 
  Being in the public domain is not a license--rather, it means the material is 
  not copyrighted and no license is needed. Practically speaking, though, if a 
  work is in the public domain, it might as well have an all-permissive 
  non-copyleft free software license. Public domain status is compatible with 
  the GNU GPL. 
  The Cryptix General License. 
  This is a simple, permissive non-copyleft free software license, compatible 
  with the GNU GPL. It is very similar to the X11 license. 
  The modified BSD license. 
  (Note: on the preceding link, the modified BSD license is listed in the 
  "General" section.) 
  This is the original BSD license, modified by removal of the a