The Debian Free Software Guidelines (DFSG) are a set of guidelines that the Debian Project uses to determine whether a software license is free software license, which in turn is used to determine whether a piece of software can be included in the main, free software distribution of Debian. Debian had by 2003 collected over seven and a half thousand software packages compliant with the above guidelines.

The guidelines state these requirements:

• free redistribution
• inclusion of source code
• allowing for modifications and derived works to be made under the same license
• integrity of the author's source code (as a compromise for the likes of TeX)
• no discrimination against persons or groups
• no discrimination against fields of endeavor, like commercial use
• distribution of license, it needs to apply to all to whom the program is redistributed
• license must not be specific to Debian, basically a reiteration of the last point
• license must not contaminate other software

Example licenses are GPL, BSD, and Artistic.

The Open Source Definition was created from the DFSG.

Most discussion about the DFSG happens on the debian-legal mailing list. When the maintainers of the individual packages first upload packages into the Debian archive, the Debian ftpmaster team evaluates the software licenses and decides whether they are in accordance with the DFSG. The ftpmasters tend to confer with the debian-legal list with controversial cases.

debian-legal tests for DFSG compliance

The debian-legal mailing list subscribers have created some tests to check whether a license passes the DFSG. The common tests (as described in the FAQ) are the following:

• The Desert Island test. Imagine a castaway on a desert island with a solar-powered computer. This would make it impossible to fulfill any requirement to make changes publicly available or to send patches to some particular place. This holds even if such requirements are only upon request, as the castaway might be able to receive messages but be unable to send them. To be Free, software must be modifiable by this unfortunate castaway, who must also be able to legally share modifications with friends on the island.
• The Dissident test. Consider a dissident in a totalitarian state who wishes to share a modified bit of software with fellow dissidents, but does not wish to reveal the identity of the modifier, or directly reveal the modifications themselves, or even possession of the program, to the government. Any requirement for sending source modifications to anyone other than the recipient of the modified binary -- in fact any forced distribution at all, beyond giving source to those who receive a copy of the binary -- would put the dissident in danger. For Debian to consider software Free it must not require any such excess distribution.
• The Tentacles of Evil test. Imagine that the author is hired by a large evil corporation and, now in their thrall, attempts to do the worst to the users of the program: to make their lives miserable, to make them stop using the program, to expose them to legal liability, to make the program non-Free, to discover their secrets, etc. The same can happen to a corporation bought out by a larger corporation bent on destroying Free software in order to maintain its monopoly and extend its evil empire. The license cannot allow even the author to take away the required freedoms!

The group also examines practical problems, such as GPL incompatibility.

Debian developers also argue that the same principles should apply not only to programs, but to software documentation as well. Much documentation written by the Linux Documentation Project, and many documents licensed under the GNU Free Documentation License (the documents with invariant sections), fail to comply with all of the above guidelines.

External links

• Debian Social Contract and Free Software Guidelines
• debian-legal list, with archives from previous discussions
• Draft DFSG FAQ
• Other license issues section of "Why OSS/FS? Look at the Numbers!" identifies some of the major issues discussed by debian-legal.