Categories of free and nonfree software
Also see Confusing
Words which You Might Want to Avoid.
This diagram, originally by Chao-Kuei and updated by several
others since, explains the different categories of software. It's
available as a Scalable Vector
Graphic and as an XFig
document, under the terms of any of the GNU GPL v2 or later,
the GNU FDL v1.2 or later, or the Creative Commons
Attribution-Share Alike v2.0 or later.
Free software is software that comes with permission for
anyone to use, copy, and/or distribute, either verbatim or with
modifications, either gratis or for a fee. In particular, this
means that source code must be available. “If it's not
source, it's not software.” This is a simplified
description; see also
If a program is free, then it can potentially be included
in a free operating system such as GNU, or free versions of
There are many different ways to make a program free—many
questions of detail, which could be decided in more than one way
and still make the program free. Some of the possible variations
are described below. For information on specific free software
licenses, see the license
Free software is a matter of freedom, not price. But
proprietary software companies typically use the term
“free software” to refer to price. Sometimes they
mean that you can obtain a binary copy at no charge; sometimes
they mean that a copy is bundled with a computer that you are
buying, and the price includes both. Either way, it has
nothing to do with what we mean by free software in the GNU
Because of this potential confusion, when a software company
says its product is free software, always check the actual
distribution terms to see whether users really have all the
freedoms that free software implies. Sometimes it really is free
software; sometimes it isn't.
Many languages have two separate words for
“free” as in freedom and “free” as in
zero price. For example, French has “libre” and
“gratuit”. Not so English; there is a word
“gratis” that refers unambiguously to price, but
no common adjective that refers unambiguously to freedom. So
if you are speaking another language, we suggest you translate
“free” into your language to make it clearer. See
our list of
translations of the term “free software” into
various other languages.
Free software is often more
reliable than nonfree software.
Open source software
The term “open source” software is used by some
people to mean more or less the same category as free
software. It is not exactly the same class of software: they
accept some licenses that we consider too restrictive, and
there are free software licenses they have not
accepted. However, the differences in extension of the
category are small: nearly all free software is open source,
and nearly all open source software is free.
We prefer the term “free
software” because it refers to
freedom—something that the term “open
source“ does not do.
Public domain software is software that is not copyrighted. If
the source code is in the public domain, that is a special case of
software, which means that some copies or modified versions
may not be free at all.
In some cases, an executable program can be in the public domain
but the source code is not available. This is not free software,
because free software requires accessibility of source code.
Meanwhile, most free software is not in the public domain; it is
copyrighted, and the copyright holders have legally given
permission for everyone to use it in freedom, using a free software
Sometimes people use the term “public domain”
in a loose fashion to
mean “free” or
“available gratis.” However, “public
domain” is a legal term and means, precisely, “not
copyrighted”. For clarity, we recommend using
“public domain” for that meaning only, and using
other terms to convey the other meanings.
Under the Berne Convention, which most countries have
signed, anything written down is automatically
copyrighted. This includes programs. Therefore, if you want a
program you have written to be in the public domain, you must
take some legal steps to disclaim the copyright on it;
otherwise, the program is copyrighted.
Copylefted software is free software whose distribution
terms ensure that all copies of all versions carry more or
less the same distribution terms. This means, for instance,
that copyleft licenses generally disallow others to add
additional requirements to the software (though a limited set
of safe added requirements can be allowed) and require making
source code available. This shields the program, and its
modified versions, from some of the common ways of making a
Some copyleft licenses, such as GPL version 3, block
other means of turning software proprietary, such as tivoization.
In the GNU Project, we copyleft almost all the software we
write, because our goal is to give every user the freedoms
implied by the term “free software.” See our copyleft article for more explanation of
how copyleft works and why we use it.
Copyleft is a general concept; to copyleft an actual program,
you need to use a specific set of distribution terms. There are
many possible ways to write copyleft distribution terms, so in
principle there can be many copyleft free software licenses.
However, in actual practice nearly all copylefted software uses the
GNU General Public
License. Two different copyleft licenses are usually
“incompatible”, which means it is illegal to merge
the code using one license with the code using the other
license; therefore, it is good for the community if people use
a single copyleft license.
Noncopylefted free software
Noncopylefted free software comes from the author with
permission to redistribute and modify, and also to add additional
restrictions to it.
If a program is free but not copylefted, then some copies
or modified versions may not be free at all. A software
company can compile the program, with or without
modifications, and distribute the executable file as
a proprietary software
The X Window System
illustrates this. The X Consortium releases X11 with
distribution terms that make it noncopylefted free
software. If you wish, you can get a copy which has those
distribution terms and is free. However, there are nonfree
versions as well, and there are (or at least were) popular
workstations and PC graphics boards for which nonfree
versions are the only ones that work. If you are using this
hardware, X11 is not free software for
you. The developers of X11 even
made X11 nonfree for a while; they were able to do this
because others had contributed their code under the same
Lax permissive licensed software
Lax permissive licenses include the X11 license and the
two BSD licenses. These licenses permit
almost any use of the code, including distributing proprietary
binaries with or without changing the source code.
The GNU GPL (General Public
License) is one specific set of distribution terms for
copylefting a program. The GNU Project uses it as the distribution
terms for most GNU software.
To equate free software with GPL-covered software is therefore
The GNU operating system
The GNU operating system is the
Unix-like operating system, which is entirely free software, that
we in the GNU Project have developed since 1984.
A Unix-like operating system consists of many programs. The
GNU system includes all of the offical
GNU packages. It also includes many other packages, such as
the X Window System and TeX, which are not GNU software.
The first test release of the complete GNU system was in
1996. This includes the GNU Hurd, our kernel, developed since
1990. In 2001 the GNU system (including the GNU Hurd) began
working fairly reliably, but the Hurd still lacks some
important features, so it is not widely used. Meanwhile,
the GNU/Linux system,
an offshoot of the GNU operating system which uses Linux as
the kernel instead of the GNU Hurd, has been a great success
since the 90s. As this shows, the GNU system is not a single
static set of programs; users and distributors may select
different packages according to their needs and desires. The
result is still a variant of the GNU system.
Since the purpose of GNU is to be free, every single
component in the GNU operating system is free
software. They don't all have to be copylefted, however; any
kind of free software is legally suitable to include if it
helps meet technical goals.
“GNU programs” is equivalent
to GNU software. A program Foo is a
GNU program if it is GNU software. We also sometimes say it
is a “GNU package”.
GNU software is
software that is released under the auspices of the GNU Project. If a program is GNU
software, we also say that it is a GNU program or a GNU
package. The README or manual of a GNU package should say it
is one; also, the Free Software
Directory identifies all GNU packages.
Most GNU software is copylefted, but not all; however,
all GNU software must be free
Some GNU software was written by staff of
the Free Software
Foundation, but most GNU software comes from many
volunteers. (Some of these
volunteers are paid by companies or universities, but they are
volunteers for us.) Some contributed software is copyrighted
by the Free Software Foundation; some is copyrighted by the
contributors who wrote it.
FSF-copyrighted GNU software
The developers of GNU packages can transfer the copyright
to the FSF, or they can keep it. The choice is theirs.
If they have transfered the copyright to the FSF, the program
is FSF-copyrighted GNU software, and the FSF can enforce
its license. If they have kept the copyright, enforcing the license
is their responsibility.
The FSF does not accept copyright assignments of software
that is not an official GNU package, as a rule.
Nonfree software is any software that is not free.
Its use, redistribution or modification is prohibited, or
requires you to ask for permission, or is restricted so much
that you effectively can't do it freely.
Proprietary software is another name for nonfree software.
In the past we subdivided nonfree software into
“semifree software”, which could be modified and
redistributed noncommercially, and “ proprietary
software”, which could not be. But we have dropped that
distinction and now use “proprietary software” as
synonymous with nonfree software.
The Free Software Foundation follows the rule that we cannot
install any proprietary program on our computers except temporarily
for the specific purpose of writing a free replacement for that
very program. Aside from that, we feel there is no possible excuse
for installing a proprietary program.
For example, we felt justified in installing Unix on our
computer in the 1980s, because we were using it to write a free
replacement for Unix. Nowadays, since free operating systems are
available, the excuse is no longer applicable; we do not use any
nonfree operating systems, and any new computer we install
must run a completely free operating system.
We don't insist that users of GNU, or contributors to GNU, have
to live by this rule. It is a rule we made for ourselves. But we
hope you will follow it too, for your freedom's sake.
The term “freeware” has no clear accepted
definition, but it is commonly used for packages which permit
redistribution but not modification (and their source code is
not available). These packages are not free software,
so please don't use “freeware” to refer to free
Shareware is software which comes with permission for people to
redistribute copies, but says that anyone who continues to use a
copy is required to pay a license fee.
Shareware is not free software, or even semifree. There are two
reasons it is not:
- For most shareware, source code is not available; thus, you
cannot modify the program at all.
- Shareware does not come with permission to make a copy and
install it without paying a license fee, not even for individuals
engaging in nonprofit activity. (In practice, people often
disregard the distribution terms and do this anyway, but the terms
don't permit it.)
Private or custom software is software developed for one user
(typically an organization or company). That user keeps it and uses
it, and does not release it to the public either as source code or
A private program is free software (in a somewhat trivial
sense) if its sole user has the four freedoms. In particular,
if the user has full rights to the private program, the program is
free. However, if the user distributes copies to others and does
not provide the four freedoms with those copies, those copies
are not free software.
Free software is a matter of freedom, not access. In
general we do not believe it is wrong to develop a program and
not release it. There are occasions when a program is so
important that one might argue that withholding it from the
public is doing wrong to humanity. However, such cases are
rare. Most programs are not that important, and declining to
release them is not particularly wrong. Thus, there is no
conflict between the development of private or custom software
and the principles of the free software movement.
Nearly all employment for programmers is in development of
custom software; therefore most programming jobs are, or could be,
done in a way compatible with the free software movement.
“Commercial” and “proprietary” are
not the same! Commercial software is software developed by a
business as part of its business. Most commercial software
is proprietary, but there
is commercial free software, and there is noncommercial
For example, GNU Ada is developed by a company. It is always
distributed under the terms of the GNU GPL, and every copy is
free software; but its developers sell support contracts. When
their salesmen speak to prospective customers, sometimes the
customers say, “We would feel safer with a commercial
compiler.” The salesmen reply, “GNU
Ada is a commercial compiler; it happens to be free
For the GNU Project, the priorities are in the other order:
the important thing is that GNU Ada is free software; that
it is commercial is just a detail. However, the additional
development of GNU Ada that results from its being commercial
is definitely beneficial.
Please help spread the awareness that free commercial
software is possible. You can do this by making an effort not
to say “commercial” when you mean