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Purpose and Intended Audience

This page provides a history of the answers to questions asked on the legal-discuss@ mailing list, and the scope of those answers. As each answer is as much dictated by Apache Software Foundation (ASF) policy as any other interpretation, it is of most value to ASF projects.

Software License Criteria

The following criteria serve as guidelines for the answers on this page.

  1. The license must meet the Open Source Definition, (latest review 2019-02-16).
  2. The license must not place restrictions on the distribution of independent works that simply use or contain the covered work.
  3. The license must not place restrictions on the distribution of larger works, other than to require that the covered component still complies with the conditions of its license.

Asking Questions

Please submit questions to the Legal Affairs Committee JIRA space.

What can we include in an ASF Project (Category A)?

For the purposes of being included in an Apache product, which licenses are considered to be similar in terms to the Apache License 2.0?

Works under the following licenses may be included within Apache products:

Many of these licenses have specific attribution terms that need to be adhered to, often by adding them to the NOTICE file. Ensure you are doing this when including these works. Note, this list is colloquially known as the Category A list.

Additionally see the question on Public Domain statements for other 'licenses' that fall within this Category A list.

Does the Yahoo! DomainKeys Patent License Agreement v1.2 raise any concerns?


Can Works Placed In The Public Domain Be Included In Apache Products?

Works in the public domain (or covered by a license treated similarly) may be included within Apache products. Attribution is required (in a similar fashion to permissive licenses).

A work should be treated as being in the public domain when one of the following applies:

Licenses that should be treated as similar to public domain:

Note that whether a work falls in the public domain may be a difficult subject. Determining whether the copyright in a work has expired may be non-trivial and may vary between jurisdictions. Raise the topic on legal-discuss@ or via a JIRA issue if you have doubt over whether a work falls in the public domain.

What can we NOT include in an ASF Project (Category X)?

Which licenses may NOT be included within Apache products?

This list is colloquially known as the Category X list. Further discussion of disallowed licenses:

Oracle's (originally Sun's) range of Binary Code License fall far short of the Open Source Definition, thereby violating the first criterion for license approval.
Discussion of Apache License v2.0 and GPL Compatibility merits a separate page.
The LGPL is ineligible primarily due to the restrictions it places on larger works, violating the third license criterion.
Special exceptions to the GNU GPL
Some copyright holders have licensed their works under the GPL with special exceptions. Although these exceptions may appear to be addressing the restrictions disallowed by the ASF's first and second license criteria, the exceptions may only apply to software not "derived from or based on" the covered work. This references terms defined in the GPL that include works that "use" or "contain" the work.
Due to restrictions (see 5.d and 5.f), falls short of the Open Source Definition, thereby violating the first criterion for license approval.
Field of use restrictions
Some licenses restrict the uses to which software licensed under them may be used. Two examples that limit use to company platforms are the Microsoft Limited Public License and the Amazon Software License.
Non-commercial licenses
Another form of limitation on field of use is a non-commercial license. Common examples are the range of Creative Commons licenses with the Non-Commercial (NC) clauses included.
Facebook BSD+Patents license
The Facebook BSD+Patents license includes a specification of a PATENTS file that passes along risk to downstream consumers of our software imbalanced in favor of the licensor, not the licensee, thereby violating our Apache legal policy of being a universal donor. The terms of Facebook BSD+Patents license are not a subset of those found in the ALv2, and they cannot be sublicensed as ALv2.
The Netscape Public License is the original license for Mozilla containing amendments that are specific to Netscape. These amendments allow "Netscape" (now part of AOL) to avoid the reciprocity requirement that all other licensees must adhere to. This disqualifies the license from meeting Open Source Definition #5 ("No Discrimination Against Persons or Groups").
Nonsensical licenses
These licenses while amusing to their creators are legally problematic. They often include subjective Field of use restrictions e.g. “Don’t be evil” with no arbiter for that subjective restriction defined. In some cases they may not even grant sufficient rights to conform to the OSI open source definition. Since we do not wish to surprise our downstream consumers we forbid the use of such licenses.

Can Apache products include works licensed under the JSON license?

No. As of 2016-11-03 this has been moved to the 'Category X' license list. Prior to this, use of the JSON Java library was allowed. See Debian's page for a list of alternatives.

Can Apache projects distribute components under prohibited licenses?

Apache projects cannot distribute any such components. This means that no source code can be from Category X and that any convenience binaries produced may not include such contents. As with the previous question on platforms, the component can be relied on if the component's license terms do not affect the Apache product's licensing. For example, using a GPL'ed tool during the build is OK, however including GPL'ed source code is not.

Can Apache projects rely on components under prohibited licenses?

Apache projects cannot distribute any such components within their releases. However, if the component is only needed for optional features, a project can provide the user with instructions on how to obtain and install the non-included work. Optional means that the component is not required for standard use of the product or for the product to achieve a desirable level of quality. The question to ask yourself in this situation is:

What can we maybe include in an ASF Project (Category B)?

How should "Weak Copyleft" Licenses be handled?

Each license in this category requires some degree of reciprocity or other restriction on use (e.g., an anti-DRM provision); this may mean that additional action is warranted in order to minimize the chance that a user of an Apache product will create a derivative work of a differently-licensed portion of an Apache product without being aware of the applicable requirements.

Software under the following licenses may be included in binary form within an Apache product if the inclusion is appropriately labeled (see below):

By including only the object/binary form, there is less exposed surface area of the third-party work from which a work might be derived; this addresses the second guiding principle of this policy.

By attaching an appropriate and prominent label to the distribution, and requiring an explicit action by the user to get the reciprocally-licensed source, users are less likely to be unaware of restrictions significantly different from those of the Apache License. Please include the URL to the product's homepage in the prominent label. An appropriate and prominent label is a label the user will read while learning about the distribution - for example in a README. Please also ensure to comply with any attribution/notice requirements in the specific license in question.

For small amounts of source that is directly consumed by the ASF product at runtime in source form, and for which that source is unmodified and unlikely to be changed anyway (say, by virtue of being specified by a standard), inclusion of appropriately labeled source is also permitted. An example of this is the web-facesconfig_1_0.dtd, whose inclusion is mandated by the JSR 127: JavaServer Faces specification.

This is colloquially known as the Category B list.

Can Apache projects have external dependencies on Ruby licensed works?

A project written primarily and obviously in Ruby can have a dependency either on Matz's Ruby Interpreter (MRI), or on any Gem which is licensed under the Ruby license.
Of course Gems written under other licenses (such as MIT) may also be OK, depending on the license.

Also note that the Ruby license is listed on the 'Category B' Weak Copyleft list below for binary usage (for example JRuby).

Can Apache projects include Creative Commons Attribution-Share Alike works?

Unmodified media under the Creative Commons Attribution-Share Alike 2.5, Creative Commons Attribution-Share Alike 3.0 and Creative Commons Attribution-Share Alike 4.0 licenses may be included in Apache products, subject to the licenses attribution clauses which may require LICENSE/NOTICE/README changes. For any other type of CC-SA licensed work, please contact the Legal PMC.

Doug Lea's concurrent library is public domain, but contains some Sun files which are not public domain. Can this be included in an Apache product?

Yes, treat it much as you currently would the Category B licenses above - "it may be included in binary form within an Apache product if the inclusion is appropriately labeled". If using the source, remove the files Sun licensed to Doug and treat as Category A (or get the files from Harmony).

Can OSGi metadata be added to weak copyleft binaries - thus modifying the binary jar file?

Insertion of OSGi metadata into 'Category B' licensed jars is permitted; even though that metadata becomes licensed under the 3rd party license when it is put in the jar, assuming that a note that this has occurred is included in the prominent labeling that the Category B language calls for.

Can Cobertura reports be included in Apache distributions?


How should licenses that prevent modification be handled?

There are licenses that give broad rights for redistribution of unmodified copies. Such licenses are not open source, but they do satisfy the second and third guiding principles above.

Apache projects must not include material under such licenses in version control or in released source packages. It is however acceptable for a build process to automatically download such non-software materials like fonts and standardized data and include them in the resulting binaries. Such use makes it clear that these dependencies are not a part of the open source code of the project.

Material under the following licenses may be used as described above:

Can build tools be included in ASF distributions?

Many languages have developed an ecosystem of associated tools that aid in the building of artifacts for distribution. While such tools may not always be made available under an otherwise compatible license, specific tools have been OK'ed for inclusion in Apache distributions when used for that specific purpose.

The most important criteria to be included in this category is that such tools are not customarily part of distributions of running code, unless such deliverables include source anyway. Other criteria for inclusion include: having been around for years, being defacto standards in their respective communities, being made available under are under "library" or "lesser" licenses or otherwise containing an exception which ensures that usage of this tool does not affect the license of the code against which it is run.

To date, the following tools have been approved for such usage:

Can we include Perl licensed header files when creating dynamically loaded XS modules?

Yes (LEGAL-79). Developing Perl bindings which link compiled C code to create dynamically loaded XS modules requires including header files licensed under the Perl license (http://dev.perl.org/licenses/ - GPL-any/Artistic1, with exceptions). You may include these header files - XSUB.h, perl.h and EXTERN.h.

Can we use Doxygen-generated config files?

As long as the generated comments are removed from the Doxygen-generated files, these files may be used.

Other Questions:

Does it matter what platform an Apache product is created to work with?

It does not matter, unless the terms for that platform affect the Apache product's licensing. For example, creating a product that runs on Windows or Java, uses a web service such as Google Services or Yahoo Search, or is a plugin for a product such as JBoss or JIRA is fine, whereas creating a Linux kernel module is not fine because the Apache product itself would have to be licensed under something other than the Apache License, version 2.0.

Note that this does not mean the platform code itself can be redistributed. That of course will depend on the licensing of said code. Also, if you have any doubts as to whether the licensing of the platform would affect the Apache code, we recommend that you check the legal-discuss@ archives to see if it has come up before, and if not email legal-discuss@ to find out.

Is IP clearance required for library dependencies?


IP clearance is used to import code bases from outside Apache for future development here.

How should works for which multiple mutually exclusive licenses are available be handled?

When including that work's licensing, state which license is being used and include only the license that you have chosen. Prefer Category A to Category B to Category X. You don't need to modify the work itself if, for example, it mentions the various licensing options in the source headers.

What Are Required Third-party Notices?

When a release contains third party works, the licenses covering those works may ask that consumers are informed in certain specific fashions. These third party notices vary from license to license. Apache releases should contain a copy of each license, usually contained in the LICENSE document. For many licenses this is a sufficient notice. For some licenses some additional notice is required. In many cases, this will be included within the dependent artifact.

A required third-party notice is any third party notice which isn't covered by the above cases.

See Bundling Other ASF Products for a note on required notices when a release contains another Apache product.