Defining Open Source

During the discussions around European digital agenda legislation, I have frequently heard people proposing to define “open source” within a draft instrument. But that's a surprisingly difficult thing to do – it turns out that despite being a globally-understood term-of-art, capturing the whole thing in a phrase simple enough to use in a recital requires a great deal of thought and experience.

So people mostly defer to the OSI Open Source Definition, which is not designed for that purpose. This post considers three different ways to consider open source — knowing it when you see it, knowing it by its goals and knowing it by summarising its mechanism — and includes a recital-ready definition of open source for use in legislation that embodies the global consensus of its meaning.

Gold-coloured figure of a traffic policeman halting traffic, pictured on a glass surface above a keyboard

Ultimately software freedom is a matter of personal liberty. Whether you describe it as “open source” or “free software”, the goal is for each individual user of software to be self-sovereign in their software and data. Any definition of open source needs to feed that confidence rather than create uncertainty by empowering control-points and gatekeepers. A precise definition has proved very hard — most attempts require some form of gatekeeper authority that ironically kills stochastic confidence.

The Open Source Definition (OSD) which OSI administers is a clever benchmark for evaluating whether licenses grant open source software freedoms. Rather than define open source precisely, it follows the “know it when you see it” principle and describes the attributes of a license that delivers software freedom. By doing so, it evades many rhetorical games. Community comparison of licenses against the OSD as a benchmark, together with OSI's role facilitating and memorialising rather than gatekeeping, has led to the overwhelming success of open source over the last 25 years.

But sometimes — increasingly often — we need a summary phrase in a recital that defines the mechanism of open source. It's important we offer text that does so in a way that reflects the expectation of the global community of communities who use “open source” as a term-of-art. Locally-sourced “definitions” are frequently incomplete, or focus on licensing as an end rather than a means, or serve the agenda of groups seeking to fragment or even subvert the community.

Ideally we would say that “open source software is software released under an OSI-approved license.” This definition would perfectly encapsulate the global consensus without creating any new “games” to be played. But we have found that governments do not want to make normative references to any organisation they cannot control. OSI is an independent, global, public charity so certainly cannot be controlled!

I believe this phrase expresses almost the same idea without mentioning an organisation:

Open source software is software released under a license that — by broad community consensus — grants all rights necessary to use, adapt, share and monetise the software in any way and for any purpose subject only to conditions that can be reasonably satisfied without negotiation with the licensors.

In spite of all this, I still think it is better to embrace all three lenses — reference the OSD and the community consensus process OSI crystallizes, state the goals and summarise with the summary phrase — if you are able to do so.


I'll be pleased to have suggestions that improve this phrase without making it significantly longer or more complex. If you're going to try improving it, here's why I've used each element:

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