Libre Software definition
Libre Software (Free Software) was defined by the GNU proyect.
Libre Software users enjoy the following four freedoms, granted by the license under which it is published:
Freedom 0: the freedom to use the program for whatever the user wants.
The user may use he program for whatever he wishes, without requiring being granted permission by the author.
Freedom 1: the freedom to study the program code, and to modify it.
In order to enjoy this freedom, the user needs access to the source code of the program. If the source code is not clear and can not be studied in practice, that code can not be considered the source code.
In order to be considered libre (free), the program must permit effective modification, and there must not be barriers or restrictions for it to be merged with other routines or libre programs.
Freedom 2: the freedom to redistribute copies of the program.
The user must be able to redistribute copies of the programs, in useable or runnable form as well as in source code form.
Freedom 3: the freedom to redistribute copies of modified versions.
The user must be able to redistribute copies of a modified version of the program. If the program's license requires that the redistributed versions be privative, then the program is not libre.
To be able to enjoy this freedom, the user needs to have access to the source code of the program.
Conditions that a program must meet in order to be considered libre:
A program is Libre Software if it respects the four freedoms. In order to determien whether the program is libre, we can check:
- The license (it must be a libre license, that conveys the four freedoms, in a clear and irrevocable way. Licenses that allow partial or full reversal are not considered libre licenses.)
- The distribution (source code must be available, and modifications must be practically possible)
Libre, not gratis
Libre Software must offer the four freedoms but that does not imply neccessarily zero cost.This is a matter of freedoms and rights, not price. It is possible to charge for the development and distribution of Libre Software, and there are many related cases and business models.
Libre, not "open"
There are who name Libre Software as "open source" software. Although they can be referring to similar programs, the idea that the term "open" conveys does not include the values and rights related to freedom. The word "libre" (free) refers to that freedom and thus is a more precise and adequate term. In practice, "Libre Software" and "open source" refer mostly to the same programs, but mean, express and convey different things.