Debian Free Software Guidelines

The Debian Free Software Guidelines (DFSG) is a set of guidelines that the Debian Project uses to determine whether a software license is a free software license, which in turn is used to determine whether a piece of software can be included in Debian. The DFSG is part of the Debian Social Contract.

The GNU GPL, BSD, and Artistic licenses are examples of licenses considered free.

The DFSG was first published together with the first version of the Debian Social Contract in July 1997. The concept of providing a formal guarantee for the distribution's licensing policy was suggested by Ean Schuessler and the primary authors were Bruce Perens and several other Debian developers at the time.

The Open Source Definition was created by modifying the text of the DFSG soon afterwards. DFSG was preceded by Free Software Foundation's Free Software Definition. Once the DFSG became the Open Source Definition, Richard Stallman saw the need to differentiate free software from open source and promoted the Free Software Definition. Published versions of FSF's Free Software Definition existed as early as 1986, having been published in the first edition of the (now defunct) GNU's Bulletin. It is worth noting that the core of the Free Software Definition is the Four Freedoms, which clearly preceded the drafting and promulgation of the DFSG, but were unknown to its authors.

...
Wikipedia