Apache License
Encyclopedia
The Apache License icon is a copyfree free software license authored by the Apache Software Foundation
Apache Software Foundation
The Apache Software Foundation is a non-profit corporation to support Apache software projects, including the Apache HTTP Server. The ASF was formed from the Apache Group and incorporated in Delaware, U.S., in June 1999.The Apache Software Foundation is a decentralized community of developers...

 (ASF). The Apache License requires preservation of the copyright
Copyright
Copyright is a legal concept, enacted by most governments, giving the creator of an original work exclusive rights to it, usually for a limited time...

 notice and disclaimer
Disclaimer
A disclaimer is generally any statement intended to specify or delimit the scope of rights and obligations that may be exercised and enforced by parties in a legally recognized relationship...

.

All software produced by the ASF or any of its projects or subjects is licensed according to the terms of the Apache License. Some non-ASF software is also licensed using the Apache License. As of November 2010, over 6000 projects located at SourceForge.net
SourceForge.net
SourceForge is a web-based source code repository. It acts as a centralized location for software developers to control and manage open source software development. The website runs a version of SourceForge Enterprise Edition, forked from the last open-source version available...

 were available under the terms of the Apache License. In a blog post from May 2008 Google
Google
Google Inc. is an American multinational public corporation invested in Internet search, cloud computing, and advertising technologies. Google hosts and develops a number of Internet-based services and products, and generates profit primarily from advertising through its AdWords program...

 mentioned that 25,000 out of the 100,000 projects then hosted on Google Code
Google Code
Google Code is Google's site for developer tools, APIs and technical resources. The site contains documentation on using Google developer tools and APIs—including discussion groups and blogs for developers using Google's developer products....

 were using the Apache License.

Version history

The Apache License 1.0 was the original Apache License which applies only to older versions of Apache packages (such as version 1.2 of the Web server).

The Apache License 1.1 was approved by the ASF in 2000: The primary change from the 1.0 license is in the 'advertising clause' (section 3 of the 1.0 license); derived products are no longer required to include attribution in their advertising materials, but only in their documentation.

The ASF adopted the Apache License 2.0 in January 2004. The stated goals of the license included making the license easier for non-ASF projects to use, improving compatibility
License compatibility
License compatibility refers to the problem with licenses applied to works subject to copyright, particularly licenses of software packages, which can contain contradictory requirements, rendering it impossible to combine source code from such packages or content from such works in order to create...

 with GPL
GNU General Public License
The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU Project....

-based software, allowing the license to be included by reference instead of listed in every file, clarifying the license on contributions, and requiring a patent license on contributions that necessarily infringe a contributor's own patents
.

Licensing conditions

Like any free software license, the Apache License allows the user of the software the freedom to use the software for any purpose, to distribute it, to modify it, and to distribute modified versions of the software, under the terms of the license.

The Apache License, like most other permissive licenses, does not require modified versions
Derivative work
In United States copyright law, a derivative work is an expressive creation that includes major, copyright-protected elements of an original, previously created first work .-Definition:...

 of the software to be distributed using the same license (in contrast to copyleft
Copyleft
Copyleft is a play on the word copyright to describe the practice of using copyright law to offer the right to distribute copies and modified versions of a work and requiring that the same rights be preserved in modified versions of the work...

 licenses). In every licensed file, any original copyright, patent, trademark, and attribution notices in redistributed code must be preserved (excluding notices that do not pertain to any part of the derivative works); and, in every licensed file changed, a notification must be added stating that changes have been made to that file.

If a NOTICE text file is included as part of the distribution of the original work, then derivative works must include a readable copy of these notices (again, excluding notices not pertaining to any part of the derivative work), in at least one of three places: within a NOTICE text file distributed as part of the derivative works, within the source form or documentation, or within a display generated by the derivative works (wherever such third-party notices normally appear). The contents of the NOTICE file do not modify the license, as they are for informational purposes only, and adding more attribution notices as addenda to the NOTICE text is permissible, provided that these notices cannot be understood as modifying the license. Modifications may have appropriate copyright notices, and may provide different license terms for the modifications.

Unless explicitly stated otherwise, any contributions submitted by a licensee to a licensor will be under the terms of the license without any terms and conditions, but this does not preclude any separate agreements with the licensor regarding these contributions.

GPL compatibility

The Apache Software Foundation and the Free Software Foundation
Free Software Foundation
The Free Software Foundation is a non-profit corporation founded by Richard Stallman on 4 October 1985 to support the free software movement, a copyleft-based movement which aims to promote the universal freedom to create, distribute and modify computer software...

 (FSF) agree that the Apache License 2.0 is a free software license, compatible with version 3 of the GNU General Public License
GNU General Public License
The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU Project....

 (GPL). Compatibility in this case means that since the GPL version 3 is considered a superset of the Apache License 2.0, a project combining GPL version 3 and Apache License 2.0 code will need to be licensed under the GPL version 3.

However, the Free Software Foundation
Free Software Foundation
The Free Software Foundation is a non-profit corporation founded by Richard Stallman on 4 October 1985 to support the free software movement, a copyleft-based movement which aims to promote the universal freedom to create, distribute and modify computer software...

 considers all versions of the Apache License (as of 2007) to be incompatible
License compatibility
License compatibility refers to the problem with licenses applied to works subject to copyright, particularly licenses of software packages, which can contain contradictory requirements, rendering it impossible to combine source code from such packages or content from such works in order to create...

with the previous GPL versions 1 and 2.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK