The Debian Administrator's Handbook

The existence of the non-free section particularly annoys the Free Software Foundation, causing it, thus, to refuse to officially recommend Debian as an operating system.

1.2.2. The Debian Free Software Guidelines

This reference document defines which software is “free enough” to be included in Debian. If a program's license is in accord with these principles, it can be included in the main section; on the contrary, and provided that free distribution is permitted, it may be found in the non-free section. The non-free section is not officially part of Debian; it is an added service provided to users.

More than a selection criteria for Debian, this text has become an authority on the subject of free software, and has served as the basis for the “Open Source definition”. It is, thus, historically one of the first formalizations of the concept of “free software”.

The GNU General Public License, the BSD License, and the Artistic License are examples of traditional free licenses that follow the 9 points mentioned in this text. Below you will find the text as it is published on the Debian website.

→ http://www.debian.org/social_contract#guidelines

Free redistribution. The license of a Debian component may not restrict any party from selling or giving away the software as a component of an aggregate software distribution containing programs from several different sources. The license may not require a royalty or other fee for such sale.

BACK TO BASICS Free licenses

The GNU GPL, the BSD license, and the Artistic License all comply with the Debian Free Software Guidelines, even though they are very different.

The GNU GPL, used and promoted by the FSF (Free Software Foundation), is the most common. A particular feature thereof is that any redistributed program or work derived from a program incorporating or using GPL code, can only be distributed according to its terms. It prohibits, thus, any reuse in a proprietary application. This poses serious problems for the reuse of GPL code in free software incompatible with this license. As such, it is sometimes impossible to link a program published under another free software license with a library distributed under the GPL. On the other hand, this license is very solid in American law: FSF lawyers have participated in the drafting thereof, and have often forced violators to reach an amicable agreement with the FSF without going to court.

→ http://www.gnu.org/copyleft/gpl.html

The BSD license is the least restrictive: everything is permitted, including use of modified BSD code in a proprietary application. Microsoft even uses it, basing the TCP/IP layer of Windows NT on that of the BSD kernel.

→ http://www.opensource.org/licenses/bsd-license.php

Finally, the Artistic License reaches a compromise between these two others: integration of code in a proprietary application is permitted, but any modification must be published.

→ http://www.opensource.org/licenses/artistic-license-2.0.php

The complete text of these licenses is available in /usr/share/common-licenses/ on any Debian system.

Source code. The program must include source code, and must allow distribution in source code as well as compiled form.

Derived works. The license must allow modifications and derived works, and must allow them to be distributed under the same terms as the license of the original software.

Integrity of the author's source code. The license may restrict source-code from being distributed in modified form only if the license allows the distribution of “patch files” with the source code for the purpose of modifying the program at build time. The license must explicitly permit distribution of software built from modified source code. The license may require derived works to carry a different name or version number from the original software (This is a compromise. The Debian group encourages all authors not to restrict any files, source or binary, from being modified).

No discrimination against persons or groups. The license must not discriminate against any person or group of persons.

No discrimination against fields of endeavor. The license must not restrict anyone from making use of the program in a specific field of endeavor. For example, it may not restrict the program from being used in a business, or from being used for genetic research.

Distribution of license. The rights attached to the program must apply to all to whom the program is redistributed without the need for execution of an additional license by those parties.