The term “Commercial Open Source Software”, or COSS, is gaining popularity, It sounds helpful, but it blurs a clear definition, hides proprietary practices, and weakens the open source commons.
Who Uses the Term and Why
I see the term COSS used by different groups:
- Big analysts and market researchers
- Investors, venture capital firms, and startups
- IT procurement teams
- Companies with open-core or dual-license models
- Companies that failed to build a sustainable business publishing open source software and added restrictions to their software licenses
Most of them use the term to mix several different ideas: the business model, the software license and the copyright. This is where the confusion starts.
What Open Source Actually Means
To understand why the term COSS makes little sense, we need to go back to the definition of open source:
- Free Software, by FSF
- Open Source, by OSI
- The Debian Free Software Guidelines (DFSG), part of the Debian Social Contract
All of them include a simple rule: open source cannot restrict how the software is used or to which purpose.
The FSF says:
“The freedom to run the program as you wish, for any purpose.”
The OSI and DFSG says:
“No discrimination against fields of endeavor.”
This means that all open source software can be used for commercial purposes. There is no such thing as “non-commercial open source software” either. If a license restricts the usage of the software in any form, it is not open source.
Some examples of licenses that are not open source because they add restrictions to, at least, the software usage, are:
A quick read of these licenses will tell you why they are not open source licenses, once you have put effort in reading and understanding the definition of open source / free software, provided above.
Why “Commercial Open Source Software” Is Misleading
The term COSS creates several problems I will try to summarise.
1.- It suggests that commercial use is something special
But it is not. Commercial use is part of the definition of open source. Labeling something as “commercial open source software” implies that non-commercial open source software exists. It does not.
2.- It mixes copyright, license and business model
In general, mixing copyright, software licenses and business models in one label is risky. Open-core, freemium, dual-license…. based business models are totally fair. But calling the whole thing “COSS” hides the proprietary aspects, which are relevant. It also confuses people who try to understand what they can or cannot do with the provided software.
3.- It assigns “commercial value” only to specific projects, like company-led projects
Some people use COSS to refer only to projects driven by a single vendor, which solely holds the copyright of the software and/or the ability to modify the license. This ignores the reality that:
- Many commercially successful open source projects are not controlled by one company
- Many companies lead commercially successful open source projects without owning all copyrights, or they face restrictions when it comes to modifying the license
- Many companies that lead open source projects build sustainable businesses without developing nor releasing proprietary code.
Yet, these projects are not considered “COSS” by many of those who use the term, making it even more confusing.
4.- It harms the open source commons
Open source is built on shared principles. The definition is part of these “commons”. When people blur or stretch the definition, they weaken the trust that has made open source what it is today. In my view, defending the definition is not about being a purist. It is about protecting the foundations that made open source successful in the first place.
Lately I see an increasing number of companies using the term COSS to hide license changes or restrictions. People repeating the term, claiming that is harmless for open source but needed for positioning their business in specific markets, while being perceived as “open”. I cannot help but being suspicious about anyone trying to blur or “qualify” the open source definition. Too may tried the same before, for their own benefit only.
My Recommendation
My suggestion is simple:
Please do not use the term Commercial Open Source Software (COSS).
And when you see someone using it, ask what they really mean. In my experience, there is a good chance they are trying to blur the facts. Personally, I do not trust the term. And I do not trust companies that use it until I check the details myself.
This post has been polished using AI. The illustrations are also created with AI
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