What's the difference between open source software and free software?

What's the difference between open source software and free software?

Free software, open source software, FOSS, FLOSS. Are they the same? Different? Does it matter?

What's the difference between open source software and free software?
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Do you use "open source software" or "free software"? Although there are different rules for free software licenses (four freedoms) and open source licenses (Open Source Definition), what is not apparent from those two sets of rules is:

  1. Both terms refer to essentially the same set of licenses and software, and
  2. Each term implies different underlying values.

In other words, although the terms "free software" and "open source software" refer to essentially the same set of licenses, they arrive at that set via different routes. (The results aren't perfectly identical, but the differences are unlikely to matter broadly.) And, even though the licenses are the same, a person's choice of terminology may imply a different emphasis in values.

The concept of "free software" was developed by Richard Stallman in the 1980s. The focus is on what the recipient of software is permitted to do with the software: "Roughly, it means that the users have the freedom to run, copy, distribute, study, change, and improve the software."

"Open source" focuses on the practical consequences enabled by these licenses: surprisingly effective collaboration on software development. Free software came first. Later, it became apparent that free software was leading to remarkable collaboration dynamics. In 1997, Eric Raymond's seminal essay "The Cathedral and the Bazaar" focused attention on the implications that free software has for software development methodology.

In "Why Open Source Misses the Point of Free Software," Stallman explains: "The two terms describe almost the same category of software, but they stand for views based on fundamentally different values. Open source is a development methodology; free software is a social movement."

Different values? Yes. But not mutually exclusive. Rather than aligning with one or the other, many people find varying degrees of resonance with the values underlying each term.

Clearing the confusion

Rather than aligning with one or the other, many people find varying degrees of resonance with the values underlying each term.
What if someone wants to refer to this type of software without specifying underlying values? Awkwardly, there is no broadly accepted term that refers to the licenses or the software that's neutral about the values implied by each term. In other words, we lack a third term that refers to that same software and same set of licenses, but doesn't take sides with respect to why that software and those licenses are significant. It may be that "open source" was initially expected to be a neutral term; however, it has developed its own implied values.

The closest to a neutral term would be FOSS (free and open source software) or FLOSS (free/libre/open source software), which have had limited success fulfilling that value-neutral role. Perhaps the existence of two such terms (with and without "L") may have diluted and thus diminished the ability of either to break out as a broadly used term.

This assortment of terms has contributed to confusion. Would a neutral term be useful? Or is the attempt to separate the associated values a flawed goal? Is a neutral term inappropriate because there are significant free software projects that would not be considered open source? Or the reverse? Please share your thoughts in the comments.

About the author

Scott K Peterson - Scott Peterson is a member of the Red Hat legal team. Long ago, an engineer asked Scott for legal advice on a curious document known as the GPL. That fateful question began a twisting path of exploration of the legal aspects of collaborative development, including both technical standards and open source software.