I. Overview

The 2.0 version of the Apache License was approved by the Apache Software Foundation (ASF) in 2004. The goals of this license revision are to reduce the number of frequently asked questions, to allow the license to be reusable without modification by any project (including non-ASF projects), and to require a patent license in order to protect any contributors. Any software developed by the ASF before shall be switched to the Apache 2.0.

To allow this version of the Apache License compatible with other open source licenses, the ASF is still trying to make it compatible with the GPL.

 

II. Current Status

On ASF’s website, it is stated that all packages produced by the ASF are implicitly licensed under the Apache 2.0, unless otherwise explicitly stated.
 
III. Rights and Duties
 
 1. Licensee’s Rights
 
With regards to the grant of licenses, copyright and patent shall be discussed separately.
 
    (1) Grant of Copyright License
 
A perpetual, worldwide, non-exclusive, no-charge, royalty-free and irrevocable copyright license to reproduce is granted. The rights to prepare derivative works of, publicly display, publicly perform, sublicense, and distribute the Work are also granted by each contributor.
 
    (2) Grant of Patent License
 
A perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable patent license to make, have made, use, offer to sell, sell, import, and otherwise transfer the work is granted. Any patent licenses granted under this license for that work shall terminate as of the date when a patent litigation against any entity alleging patent infringement is filed by the licensee.
 
 2. Licensee’s Duties
 
The following four conditions have to be met.
 
    (1) A copy of this license must be included with the work or derivative Works; and
 
    (2) Notices stating that the licensee has changed the files must be carried in any modified files; and
 
    (3) Excluding those notices that do not pertain to any part of the derivative works, the licensee must retain, in the source form of any derivative works that he distributes, all copyright, patent, trademark, and attribution notices from the source form of the work; and
 
    (4) Excluding those notices that do not pertain to any part of the derivative works, any derivative works that the licensee distribute must include a readable copy of the attribution notices contained within a notice file, in at least one of the following places, should the work includes such a notice text file:
 
        (A) within a notice text file distributed as part of the derivative works;

        (B) within the source form or documentation, if provided along with the derivative works; or,

        (C) within a display generated by the derivative works, if and wherever such third-party notices appear. When the contents of the notice text file are for informational purposes only and do not modify the license, the licensee may add his own attribution notices within derivative works that he distributes.
 
IV. Other Important Features—Trademark, Warranty and Liability Clauses
 
 1. Limited license of trademark use: Except as required for describing the origin of the work and reproducing the content of the notice file, the Apache 2.0 does not grant permission to use the trade names, trademarks, service marks, or product names of the Licensor.
 
 2. Disclaimer of Warranty and Limitation of Liability:While redistributing the work or derivative works thereof, the licensee is free to choose to offer warranty or other liability obligations.
 
 3. The Apache 2.0 is a free sofeware license approved by Free Software Foundation (FSF), and is approved by the Open Source Initiative (OSI) as an open source license as well. It is, however, incompatible with the GPL.