Some people struggle to understand the distinctions between ‘free software’ and ‘open source software.’ Let’s clear up the confusion with an analogy.

Imagine a world without vegetarianism. One day, someone proposes a new diet called ‘moral eating,’ which excludes meat for ethical reasons. Some people embrace it, and discover additional benefits like reduced environmental impact. However, advocates observe that implying people not adhering to the diet are immoral isn’t the best recruitment strategy. They coin the term ‘sustainable eating’ to focus on the environmental advantages.

But now people get bogged down in philosophical debates. If one uses the term ‘moral eating’ some assume they don’t care about the environment; on the other hand, if one says ‘sustainable eating’ some assume they don’t care about animals. To avoid this an all-encompassing acronym MSE (Moral and Sustainable Eating) is created. It signifies the same thing — no meat — but avoids getting entangled in justifications.

And so we end up with three distinct terms — moral eating, sustainable eating and MSE — which all refer to the same diat. What we call vegetarianism.

This is how the terms free software, open source and FOSS (Free and Open Source Software) came to be. They all represent the same category of software with a different advocacy philosophy. Free software emphasises the four essential freedoms and open source uses the Open Source Definition. While the latter might be more explicit on some points — it overtly prohibits discrimination against any people or field of endeavour — the four freedoms implicitly cover them as well.

Source-available software

Here’s where things get tricky. Some companies try to capitalize on the positive associations of open source without truly adhering to its principles. They might ‘open their software’ but release source code under a license that restricts creating derivative works. This could be due to genuine misunderstanding or intentional manipulation. Whatever the reason, if the four essential freedoms aren’t granted, the code isn’t open source. This type of software is more accurately called source-available software.

Libre Software

Another point of confusion is the ambiguity of the term ‘free software.’ ‘Free’ can refer to price or freedom. The common saying ‘free as in freedom, not as in beer’ attempts to clarify this imprecision. To eliminate the ambiguity altogether, the terms libre software or libreware have emerged. And to include it in the FOSS acronym it’s sometimes replaced with FLOSS (Free, Libre and Open Source Software).

Proprietary software that one can acquire without paying is called freeware. It’s distinct from free software, which is only concerned with user freedoms and permits selling of the software.

Creative Commons and Free Software

Lastly, it’s worth mentioning the Creative Commons organisation. It aims to simplify copyright by allowing creators to share their work with specific permissions. While its goals align somewhat with free software, it’s important to note that not all Creative Commons licenses qualify. Any license that disallows derivative works (NoDerivatives) or commercial use (NonCommercial) doesn’t meet the criteria for free software.

There are three Creative Commons licenses which are considered free software:

• CC0, which is roughly equivalent to something being in Public Domain,
• CC BY (Attribution), which is roughly equivalent to permissive free software licenses and
• CC BY-SA (Attribution-ShareAlike), which is roughly equivalent to copyleft free software licenses.

However, when licensing source code, it’s generally recommended to use licenses specifically designed for software, such as various GPL variants, the Mozilla Public License, the Apache license, or the MIT license.

Conclusion

Free software, open source software, libre software, libreware, FOSS and FLOSS all describe the same category of software: software with source code that users can freely run, modify, and redistribute. Source-available software has accessible code whose license prevents one of those activities.