Free Tools

We maintain this free software definition to show clearly what must be true about a particular software program for it to be considered free software.

``Free software'' is a matter of liberty, not price. To understand the concept, you should think of ``free'' as in ``free speech,'' not as in ``free beer.''

Free software is a matter of 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.

The freedom to use a program means the freedom for any kind of person or organization to use it on any kind of computer system, for any kind of overall job, and without being required to communicate subsequently with the developer or any other specific entity.

The freedom to redistribute copies must include binary or executable forms of the program, as well as source code, for both modified and unmodified versions. (Distributing programs in runnable form is necessary for conveniently installable free operating systems.) It is ok if there is no way to produce a binary or executable form for a certain program (since some languages don't support that feature), but you must have the freedom to redistribute such forms should you find or develop a way to make them.

In order for the freedoms 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.

One important way to modify a program is by merging in available free subroutines and modules. If the program's license says that you cannot merge in an existing module, such as if it requires you to be the copyright holder of any code you add, then the license is too restrictive to qualify as free.

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, without your doing anything to give 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.

You may have paid money to get copies of free 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, even to sell copies.

``Free software'' does not mean ``non-commercial''. A free program must be available for commercial use, commercial development, and commercial distribution. Commercial development of free software is no longer unusual; such free commercial software is very important.

Rules about how to package a modified version are acceptable, if they don't substantively block your freedom to release modified versions, or your freedom to make and use modified versions privately. Rules that ``if you make your version 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 publish your version at all.) Rules that require release of source code to the users for versions that you put into public use are also acceptable. It is also acceptable for the license to require that, if you have distributed a modified version and a previous developer asks for a copy of it, you must send one, or that you identify yourself on your modifications.

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.

See Categories of Free Software 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.

Most free software licenses are based on copyright, and there are limits on what kinds of requirements can be imposed through copyright. If a copyright-based license respects freedom in the ways described above, it is unlikely to have some other sort of problem that we never anticipated (though this does happen occasionally). However, some free software licenses are based on contracts, and contracts can impose a much larger range of possible restrictions. That means there are many possible ways such a license could be unacceptably restrictive and non-free.

We can't possibly list all the ways that might happen. If a contract-based license restricts the user in an unusual way that copyright-based licenses cannot, and which isn't mentioned here as legitimate, we will have to think about it, and we will probably conclude it is non-free.

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.

Finally, note that criteria such as those stated in this free software definition require careful thought for their interpretation. To decide whether a specific software license qualifies as a free software license, we judge it based on these criteria to determine whether it fits their spirit as well as the precise words. If a license includes unconscionable restrictions, we reject it, even if we did not anticipate the issue in these criteria. Sometimes a license requirement raises an issue that calls for extensive thought, including discussions with a lawyer, before we can decide if the requirement is acceptable. When we reach a conclusion about a new issue, we often update these criteria to make it easier to see why certain licenses do or don't qualify.

If you are interested in whether a specific license qualifies as a free software license, see our list of licenses. If the license you are concerned with is not listed there, you can ask us about it by sending us email at .

If you are contemplating writing a new license, please contact the FSF by writing to that address. The proliferation of different free software licenses means increased work for users in understanding the licenses; we may be able to help you find an existing Free Software license that meets your needs.

If that isn't possible, if you really need a new license, with our help you can ensure that the license really is a Free Software license and avoid various practical problems.

Links

Free Office Suite: OpenOffice.org is a multiplatform and multilingual office suite and an open-source project. Compatible with all other major office suites, the product is free to download, use, and distribute. To help build the community, join us.

HTML-Kit - HTML-Kit is a full-featured, highly customizable and free development environment that can be used to create, edit, validate, preview and publish web pages and scripts.

:PostgreSQL - [an X11-style license] - PostgreSQL is a sophisticated Object-Relational DBMS, supporting almost all SQL constructs, including subselects, transactions, and user-defined types and functions. It is the most advanced open-source database available anywhere.

Dopi - Dopi is an application that allows you to update the songs stored on your Apple iPod, similar to gtkpod. It relies on my ipod-sharp library.

AKFQuiz 'AKFQuiz' lets you make your own quiz games, learning exercises or psychotests. These can be used with grquiz in a graphical environment, or with scrquiz on the text-console. There is also a line oriented variant, linequiz, which can be used as a backend. A CGI-variant, cgiquiz, can be installed on a Web server to offer exercises via Internet or a local network. Or you can use mkquiz, which generates an HTML-file for to use with JavaScript. Those can then be published using any web-space provider.

CrocoPat - 'CrocoPat' is a tool for querying and manipulating relations. It is easy to use because of its simple query and manipulation language based on predicate calculus and its simple file format for relations. It is efficient because it internally represents relations as binary decision diagrams, a data structure that is well-known as a compact representation of large relations. CrocoPat is general, because it manipulates not only graphs (i.e. binary relations), but n-ary relations.

granule - Pauker is a generic flashcard program written in Java. It uses a combination of ultra-shortterm, shortterm, and longterm memory. You can use it to learn all the things you never want to forget, like vocabulary, capitals, important dates, etc

Axiom - Axiom is a general purpose Computer Algebra system. It was originally created under the name Scratchpad and has seen development at companies such as IBM and NAG. Axiom provides a mature, powerful, strongly typed environment designed to enable research into mathematical algorithms and theory. It is also useful for engineering or scientific purposes.

Flawfinder - 'Flawfinder' looks through source code for potential security flaws in source code by using a built-in database of C/C++ functions with well-known problems, and providing a list of potential security flaws, sorted by risk, with the most potentially dangerous flaws shown first. Risk level depends on both the function and the values of the parameters of the function. It ignores text inside comments and strings.

Ding - Ding is a dictionary lookup program that uses the 'agrep' or 'egrep' tools for searching. It comes with a German-English Dictionary with ca. 120,000 entries. It is a Tk based Front-End to [ae]grep, ispell, or dict. 'Ding' can also search in English dictionaries using 'dict' and check spelling using 'ispell.' Configuration options include search preferences, interface language (English or German), and colors.

G-Cows - G-Cows is a command line tool designed to make the creation and updating of a web site faster, more flexible and less prone to errors without relying on server-side technologies (scripting languages, web server's extensions etc.).

HTML::Mason - HTML::Mason is a web site development and delivery system that constructs web pages and sites from shared, reusable building blocks called components. Components contain a mix of Perl and HTML, and can call each other and pass values back and forth like subroutines. They increase modularity and eliminate repetitive work. HTML::Mason is most powerful when used in conjunction with mod_perl, but can be used in standalone applications as well.

html2pdf - HTML_ToPDF takes the hassle out of generating a PDF file from a Web page. It will convert any HTML document into a format that will look the same on any platform and printer. It includes support for converting images, using the stylesheets to customize the look of the PDF file, and error handling.

ASPSeek- ASPSeek is an Internet search engine. It consists of an indexing robot, a search daemon, and a CGI search frontend. It Supports Webspaces, which means that the user can combine and perfrom searches within several Web sites simultaneously, instead of browsing each site individually.

Pagecast -Pagecast makes it easy to submit lists of URLs. It also has more advanced features such as the ability to check the URL's for problematic conditions. It is designed to be simple to use and effective at what it does.