FOSS stands for "Free and Open Source Software", whereas FLOSS stands for "Free/Libre/Open Source Software". The use of libre denotes the idea that the software is "free as in free speech, not free beer," as Richard Stallman put it.

What is the practical difference between FOSS and FLOSS? Does the inclusion of libre denote fewer restrictions in FLOSS, or is the difference subtler?

I found a longer explanation by Stallman, but it seems to indicate that FLOSS merely emphasizes the way the software is "free".

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    The difference is the L. The term is informal, not authoritative. The L for Libre was added to make it clearer what F(L)OSS means, not to narrow down it's meaning.
    – Martijn
    Jun 24, 2015 at 15:09

3 Answers 3


French Skills to the test!

Libre -> Free as in Freedom. I'm Free as a bird!

Gratuit -> Free as in Free Food. The Food is Free!

People started using the term FLOSS to help make the vision that the software is libre, and not free. FLOSS meant Free/Libre Open Source Software, whereas FOSS would mean Free and Open Source Software. This is less clear, as FOSS may not be interpreted with freedom. If you want to accept both, you should use FLOSS.

For More Info: Free Software, Open Source, FOSS, FLOSS - same same but different

Source: FLOSS and FOSS

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    I have to say, I read about this (it's the same link I gave).
    – HDE 226868
    Jun 24, 2015 at 15:08
  • I added an extra link if it helps! :)
    – Zizouz212
    Jun 24, 2015 at 15:10

I think FOSS and FLOSS are synonyms. (The FSF agrees, but recommends to use FLOSS.)

"Free Software" refers to The Free Software Definition, "Open Source" refers to the The Open Source Definition. The terms FOSS and FLOSS are used to refer to software that is licensed under a license that the FSF and (not or) the OSI approved.

In both cases, the "F" stands for "free", and in both cases this "free" refers to the concept of freedom, not to gratis. FOSS and FLOSS may cost money.

Adding "L" for "libre" helps to clarify this, because "free" is ambiguous in the English language. (After all, it says "free/libre", not "free and libre".)


I've partially covered this in another answer, which might be worth a read.

Libre is from the French and/or Spanish (there may be other languages too, but those come to mind). In said languages, "libre" implies, as you say, free speech not free beer.

The first difference, then, is that FLOSS is actually implied to be a bit more restrictive to the creator: i.e. categorising your software as FLOSS implies you will not charge for it. FOSS, on the other hand, doesn't specify what "free" it means, so you can charge for it.

Your users, on the other hand, won't see much of a difference apart from cost: whether software is FLOSS or FOSS, they will be able to use it in much the same way. This is as opposed to sourcing differences: the difference between open- and visible-source is large, whereas the difference between FOSS and FLOSS is small.

It seems this is the only major distinction between the two.

Stallman has also written this article, which mentions FOSS and FLOSS briefly, among other discussion of the principles of "free" software. (Thanks to Pandya for bringing this up in chat).

  • Great, thanks. Do you know if Stallman or someone else involved in the development of FOSS/FLOSS wrote something else on the subject?
    – HDE 226868
    Jun 24, 2015 at 15:05
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    I am not so sure that using the term FLOSS also implies that the software will be free of charge. Can you support that in some way? Jun 24, 2015 at 15:11
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    @Bart - libre means free as in rights. If you're saying that you'll distribute this software with free rights yet mention nothing about prices (noting you've already said 'free'), people are going to think it won't cost them. True, you could still charge for it, but the implication is that you won't.
    – ArtOfCode
    Jun 24, 2015 at 15:12
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    @ArtOfCode: I have FLOSS always understood to mean "free, in the meaning of libre, software". So the Libre in the acronym is more of a clarification on what meaning of Free you intended. Jun 24, 2015 at 15:18
  • 1
    @HDE226868 Stallman has written something else - see edits.
    – ArtOfCode
    Jun 25, 2015 at 17:09

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