I know that Free Software (this means the concept of free as in freedom, not software that does not cost anything) and Open Source have two distinct definitions. In practice though, they turn out to be mostly the same. But I was asking myself, if the minor differences can lead to a software license that is conforming to one definition but not the other? Does such an example exist? And what are the points in either definition, that make them different?


3 Answers 3



See the examples from my answer to the question "Is Open Source Software a subset of free software?":

Example 1: Free Software, but not Open Source Software

Netscape’s early versions of Mozilla were released under the Netscape Public License version 1.0 (see its Wikipedia article).

This license is approved by the FSF, but it is not approved by the OSI.

↳ So these early versions of Mozilla are Free Software, but not Open Source Software.

Example 2: Open Source Software, but not Free Software

Active Agenda is licensed under the Reciprocal Public License.

This license is approved by the OSI (currently in version 1.5), but it is not approved by the FSF (it’s listed as unfree, linking to version 1.3).

↳ So Active Agenda is Open Source Software, but not Free Software.

There are various reasons why OSI could approve a license that FSF doesn’t, and vice versa.

The "Approvals" table in the Wikipedia article 'Comparison of free and open-source software licenses' lists cases where only one of FSF and OSI approved a license, and sometimes links to a source that explains why the other organization didn’t approve it.

For example, the Do What the Fuck You Want to Public License (WTFPL) is approved by the FSF, but not by the OSI. In OSI’s Board Meeting Minutes, where this license was discussed, it says:

Mr. Nelson's report includes the following licenses to be discussed and approved/disapproved by the Board.

  1. […]

  2. Title: WTFPL Submission: http://crynwr.com/cgi-bin/ezmlm-cgi?17:mss:634:200902:aglgcgbhmfcheffmdgon License: http://sam.zoy.org/wtfpl/ Comments: It's no different from dedication to the public domain. Author has submitted license approval request -- author is free to make public domain dedication. Although he agrees with the recommendation, Mr. Michlmayr notes that public domain doesn't exist in Europe. Recommend: Reject

They decided to "reject the WFTPL as redundant to the Fair License".

  • 1
    This equates open source with "under OSI approved license", and I'm not sure that's right.
    – Martijn
    Jun 28, 2015 at 17:40
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    @Martijn: OP links to a page from the OSI, so I assumed OP is asking about the term "Open Source" as defined by the OSI. And by that definition, "Open Source" software is software licensed under a license approved by the OSI.
    – unor
    Jun 28, 2015 at 17:52
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    well, take the WTFPL from your example. It's not OSI certified, but the OSI never said it was not open source. OSI said the license was redundant to another open license, which implies they believe it's open source.
    – Martijn
    Jun 28, 2015 at 17:55
  • @Martijn: It may be the case that the WTFPL fulfills all of OSI’s requirements to become an approved license, but unless they actually approve and list it, it’s not an Open Source license. They even have a category of approved licenses which is called "Licenses that are redundant with more popular licenses", but the WTFPL is not listed there.
    – unor
    Jun 28, 2015 at 18:01
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    Maybe they mainly wanted to avoid having the word "Fuck" on any of their official material :) Jul 4, 2015 at 11:25

Comparison of free and open-source software licenses > Approvals


NASA Open Source Agreement is open source but not free software.

Quoted from: http://www.gnu.org/licenses/license-list.html#NASA:-

The NASA Open Source Agreement, version 1.3, is not a free software license because it includes a provision requiring changes to be your “original creation”. Free software development depends on combining code from third parties, and the NASA license doesn't permit this.

We urge you not to use this license. In addition, if you are a United States citizen, please write to NASA and call for the use of a truly free software license.

Also visit wikipedia article in which you can see OSI approved : yes, FSF approved : no

Points to be noted:-

  • Categories of free and nonfree software:


    The term “open source” software is used by some people to mean more or less the same category as free software. It is not exactly the same class of software: they accept some licenses that we consider too restrictive, and there are free software licenses they have not accepted. However, the differences in extension of the category are small: nearly all free software is open source, and nearly all open source software is free.

    You can see reason is approval by different foundations and their ideas (bold added).

  • How Free Software and Open Source Relate as Categories of Programs:

       / |                                            | \
      /  |                                            |  \
     /   |                                            |   \
         |                                            |
         |       Source license is GNU *GPL, Apache,  |
         |        original BSD, modified BSD,         |
    free |        X11, expat, Python, MPL, etc.,      |
         |        and executable is not tivoized      |   open source
         |                                            | 
         |                                            |
     \   |                                            |
      \  |                                            |
       \ |                                            |   /
        \----------------------------------------------  /
         |     tivoized (tyrant) devices          | O | /

From open-source-misses-the-point:

...Even if the executable is made from free source code, the users cannot run modified versions of it, so the executable is nonfree.

The criteria for open source do not recognize this issue; they are concerned solely with the licensing of the source code. Thus, these unmodifiable executables, when made from source code such as Linux that is open source and free, are open source but not free.


quoted from fear of freedom

The philosophy of open source, with its purely practical values, impedes understanding of the deeper ideas of free software; it brings many people into our community, but does not teach them to defend it. That is good, as far as it goes, but it is not enough to make freedom secure. Attracting users to free software takes them just part of the way to becoming defenders of their own freedom.

emphasis mine


Yes, it exists, even if you don't count unor's examples of recognized/nonrecognized licenses.

Free but not open source

Legally, offering a service over the Internet already means that you are distributing your software to users. So in this definition, there are tons of examples, for example Google.

But even if this is not the definition you had in mind, there are installable programs which are free to use but not open source. I don't have an exact name in my head, I think Treesheets used to be closed source once, so was the .NET framework and there are probably more, mostly historical, examples. Also many device drivers are available for free but the code is closed.

Open source but not free

If you have a very stringent definition of "not free", this is of course impossible, because open source licenses prohibit you to charge for the source code, so there is always at least one method to obtain the software for free.

But if you change the definition to "the product is generally sold for money, but the code is available under an open source license", then this is available. A prominent example is CrossOver, a gaming platform allowing to run Windows games for Mac and Linux. They have a paid model, I even think that it was a subscription. Their code is GPL licensed, and available for free. Still, there are many people who pay the price, either for the convenience of having the easy install + support, or out of a "support the guys who write the software I use" consideration. I have seen the second one happening in other cases with games, such as people paying high Humble Bundle prices for open sourced games, although sometimes I think the games were open sourced after the sale (sometimes as a direct result of the sale).

The bottom line is that the basic assumption of "nobody will pay for it if they can have it for free" is empirically shown to be as false as many other simplistic assumptions of standard economic theory. We are not Chicago's homo oeconomicus. And we happen to have examples for free-but-not-open as well as open-but-not-free software products. But they are somewhat rare, because 1) people who want to do free prefer the benefits of open source, and 2) people (and especially institutions) who want to do non free are still afraid of monetary disadvantages under open source models (and may be right, if they choose the wrong model).

  • 6
    I do not speak about free as in no cost, but as free as in freedom, defined by the Free Software Foundation.
    – Mnementh
    Jun 28, 2015 at 20:11
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    I couldn't know this before the edit. Now I guess it's not an answer. I would delete it, but first I think I'll make a meta question and use this as an example for the confusion I'd like to address.
    – rumtscho
    Jun 29, 2015 at 9:26
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    I linked the Free Software Definition from the beginning, so in my opinion the question didn't change. I only made it clearer, after I saw this generated confusion. Raising a Meta about this is good.
    – Mnementh
    Jun 29, 2015 at 9:47
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    @Mnementh Oh, I see. I didn't click the link indeed. Already wrote the Meta question, meta.opensource.stackexchange.com/questions/193. Let's see what happens there, I can delete this post when the example is no longer needed.
    – rumtscho
    Jun 29, 2015 at 9:53
  • Open source licences don't prohibit charging for source code. The source code only has to be made available to the same people that get the compiled object code, and they can legally be bundled together and sold for money. What you can't do as a distributor of O.S. code is stop other people giving it away for free.
    – bdsl
    Mar 16, 2016 at 15:11

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