About Free Software

“Free software” is software developed & published according to principles which respect the essential rights and freedoms of its users and authors — the freedom to use, study, improve, and share the software. The Free Software movement is a global community of software developers and users who collaborate to build software according to these principles.

Any software is considered free software so long as it upholds the four essential freedoms:

  1. The freedom to use the software for any purpose.
  2. The freedom to study and improve the software.
  3. The freedom to share the software.
  4. The freedom to collaborate on the software.

Software which upholds these freedoms is free software. Software which does not is non-free.

Next: The four freedoms

What is “open source” software?

Open source is a movement similar to the free software movement. The movements differ mainly in their target audience: open source is more commercial in its focus, and free software is more about the users. Nevertheless, the two movements are closely related and often work together. Each movement provides a different view of software freedom, but in practice nearly all software which is considered free software is also considered open source and vice-versa. The Open Source definition and the four freedoms are compatible with one another.

The two movements as a whole are often referred to as “free and open source software”, or “FOSS”.

Generally speaking, all open source software is free software, and vice versa.

You can learn more about open source at opensource.org.

What is “source available” software?

“Source available” software refers to any software for which the source code is available, which may or may not uphold the four freedoms. It might limit commercial use, restrict redistribution, prevent the user from modifying the software, and so on. All free and open source software is source available, but not all source available software is free software.

“Source available” software is often non-free.