Free software

Free software is software (computer program) that anyone may run, share and change, at any time, for any reason. In this case, "free" means "freedom-respecting", not "free of charge". The opposite of free software is proprietary software.

In 1984, Richard Stallman started the free software movement when he began the GNU project. Examples of free software are Linux (the kernel), Blender, OpenBSD, Inkscape and others. Wikipedia also uses free software.

 Free software and open source 
Free software is very similar, but different from open source software.

People who use the name “free software” think that computers should be more ethical and should try to help people who use computers. They think every human should have four basic rights for their programs. These are the rights to:
 Use: Use programs on their computer how they want.
 Study: Learn how the programs on their computer work.
 Change: Change programs they have on their computer to make them better.
 Share: Give programs they have on their computer to other people.

The Free software movement also says that all software should be free (as in freedom). It is because even a very small program that is proprietary can be very dangerous (it can for example spy on the user).

People who use the name “open source” refer to the same software following the same rules, but the community isn't as  strict and doesn't say that everything should be open source. They avoid the ethics and instead say the rules are good because they help companies make business.

 How free software works 
An author who wants to make their computer program free must allow other people to use it for anything (which doesn't break the law), study it, change it and share it without limits. The author does this by using a free license.

The author must not prohibit even selling their program by others or using their program for dangerous things or using it by people they don't like. This is not because the author supports bad things, but because they think that limiting user's rights is dangerous for them.

 Free software and freeware 

The word “free” in “free software” means freedom, not price. People are allowed to sell Free software, but the person who buys the software can change it, give it away or sell it too.  Free/Libre and Open-Source Software is sometimes abbreviated as FOSS or FLOSS to emphasize that it is about "free software", and not merely "freeware".

The words “free software” are sometimes used in English to just mean software that can be downloaded without paying money, which is confusing. Sometimes this software lets people make their own copies for other people, however it may not let people do all the things that they can do with real Free software, such as change it or sell it. In this case “free” means “free of charge”. To make the difference more clear, software that does not cost money should be called freeware; it is almost always proprietary software.

 References 

Related pages
GNU
Free and open-source software
Free Software Foundation
Open source

 Other websites 
 Free Software Foundation
 The definition of free software
 Richard Stallman's talk about free software at TEDx