Document from the
Free Software Foundation:
''Free software'' is a matter of liberty, not price. To understand the concept, you should think of ''free speech'', not ``free beer.''
''Free software'' refers to the users' freedom to run, copy, distribute, study, change and improve the software. More precisely, it refers to four kinds of freedom, for the users of the software:
- The freedom to run the program, for any purpose (freedom 0).
- The freedom to study how the program works, and adapt it to your needs (freedom 1). Access to the source code is a precondition for this.
- The freedom to redistribute copies so you can help your neighbor (freedom 2).
- The freedom to improve the program, and release your improvements to the public, so that the whole community benefits. (freedom 3). Access to the source code is a precondition for this.
A program is free software if users have all of these freedoms. Thus, you should be free to redistribute copies, either with or without modifications, either gratis or charging a fee for distribution, to anyone anywhere. Being
free to do these things means (among other things) that you do not
have to ask or pay for permission.
You should also have the freedom to make modifications and use them
privately in your own work or play, without even mentioning that they
exist. If you do publish your changes, you should not be required to
notify anyone in particular, or in any particular way.
In order for the freedom to make changes, and to publish improved
versions, to be meaningful, you must have access to the source code of
the program. Therefore, accessibility of source code is a necessary
condition for free software.
You may have paid money to get copies of GNU software, or you may have
obtained copies at no charge. But regardless of how you got your
copies, you always have the freedom to copy and change the software.
In order for these freedoms to be real, they must be irrevocable as
long as you do nothing wrong; if the developer of the software has the
power to revoke the license, even though you have not given cause, the
software is not free.
However, certain kinds of rules about the manner of distributing free
software are acceptable, when they don't conflict with the central
freedoms. For example, copyleft (very simply stated) is the rule that
when redistributing the program, you cannot add restrictions to deny
other people the central freedoms. This rule does not conflict with
the central freedoms; rather it protects them.
Rules about how to package a modified version are acceptable, if they
don't effectively block your freedom to release modified versions.
Rules that ``if you make the program available in this way, you must
make it available in that way also'' can be acceptable too, on the
same condition. (Note that such a rule still leaves you the choice of
whether to make the program available or not.)
In the GNU project, we use
``copyleft'' to protect these freedoms legally for everyone. But
non-copylefted free software also exists. We believe there are
important reasons why it is
better to use copyleft, but if your program is non-copylefted free
software, we can still use it.
Categories of Free Software
(18k characters)
for a description of how ``free software,'' ``copylefted software'' and
other categories of software relate to each other.
Sometimes government export control
regulations and trade sanctions can constrain your freedom to
distribute copies of programs internationally. Software developers do
not have the power to eliminate or override these restrictions, but
what they can and must do is refuse to impose them as conditions of
use of the program. In this way, the restrictions will not affect
activities and people outside the jurisdictions of these governments.
When talking about free software, it is best to avoid using terms like
``give away'' or ``for free'', because those terms imply that the
issue is about price, not freedom. Some common terms such as
``piracy'' embody opinions we hope you won't endorse. See Confusing Words and Phrases
that are Worth Avoiding for a discussion of these terms.
We also have a list of translations
of "free software" into various languages.
Another group has started using the term
open source to mean
something close (but not identical) to "free software".
Copyright (C) 1996, 1997, 1998, 1999, 2000 Free Software Foundation, Inc.,
59 Temple Place - Suite 330, Boston, MA 02111, USA
Verbatim copying and distribution of this entire article is
permitted in any medium, provided this notice is preserved.
See http://www.fsf.org/licensing/essays/free-sw.html or http://www.gnu.org/philosophy/free-sw.html.