I will frame my question with a concrete example:

HELYX is a software based on another software OpenFOAM. OpenFOAM is an open-source freely-accessible software distributed with GPLv3 licence.

HELYX advertises itself as an open-source software. However, users need to purchase the access to the source code.

In the definition of the term open source by the Open Source Initiative, the attribute of open access seems not to be mentioned.

However, according to Richard Stallman, the meaning of the term "open source" is obvious where the source code must be public/accessible for inspection.

In summary, HELYX is a ten-year-old open-source software with a pay wall. This indicates that the term open source does not always mean open access in practice.

Is my understanding correct, or there is a nuance I do miss?

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    'Open source' is not synonym for 'free'. – Tero Lahtinen Jun 26 at 9:46
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    @TeroLahtinen specifically, not a synonym for free as in free beer. – leftaroundabout Jun 27 at 11:37
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    @leftaroundabout also not a synonym for free as in free speech. – MadHatter Jun 27 at 12:08
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    Even the GPL does not require public access to the source code. It only requires you to share modifications with the people you share the binaries. AGPL is a bit more restrictive but only if you actually operate public services you need to publish it to your audience. – eckes Jun 28 at 0:48
  • 'Open source' is not synonym for 'gratis'. – CONvid19 Jun 29 at 2:39

Is my understanding correct, or there is a nuance I do miss?

There may be several, but this one is important: free software grants freedom, but not to everyone. The four freedoms are granted to all legitimate users of the software. It is perfectly OK for some organisation to sell you a copy of executable software under GPLv3. Having done so, they must not try to charge you extra for the corresponding source code (eg, s6d); nor may they try to prevent you from using and/or redistributing it under GPLv3 (ss 4, 5c).

But just because they sold you a copy under GPLv3, and (at the same time, or upon your later request) gave you the source, that does not mean they are obliged also to give your friend Bob a copy of either the source or the binary. You may give Bob a copy of the binaries, source, or both, and if you do that you must honour the requirements of GPLv3 when you do it; but neither you nor they are obliged to do so.

If a distributor charges too much money for a copy of the software, potential users may club together to buy a single copy, which they then all lawfully share, and usually it makes its way out into the wider world. Thus in practice, charging for binary access to GPL software generally only works as a business method if there is some considerable value-add. But it's perfectly acceptable to do it.

Also: the above argument only applies if the distributor is obliged to follow the GPLv3 with respect to this program by having acquired it under those terms, or having incorporated someone else's GPLv3 software into it while making it. If the distributor is the sole rightsholder1, (s)he may offer it under multiple different licences. (S)he may also offer different versions under different licences; when this happens, it's common for the non-freely-licensed version to be somewhat whizzier and slicker (the Open-Core model).

I can't find anything (yet) that confirms that Helyx is a derivative of OpenFOAM, but if it is, it may well be that it's the whizzy version of OpenFOAM, offered under less-free terms as described above; or it may well be distributed under GPLv3, but only to paying customers, also as described above. Only Helyx can tell us what's going on, and I'm not asking them.

So to answer your initial question: the rights granted by FLOSS (as per the FSF, OSI definitions) are a pure superset of those granted by open access (however that is defined). But the question is, open to whom?

1 or has permission to do this via, eg, an appropriate CLA covering all external contributions.

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    This seems about correct. A bit of googling led me to the Github project for HELYX-OS, which is described as "an open-source Graphical User Interface designed to work natively with OpenFOAM" and seems to be the open-source version of their commercial HELYX-GUI component. The other main part of their product, "HELYX-Core", is described as an "open-source CFD simulation engine developed using the OpenFOAM libraries and other open-source technologies". – Ilmari Karonen Jun 27 at 14:00
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    … Based on this, what I'd guess they're doing is following the open/core licensing model for their in-house-developed HELYX-GUI component, while distributing a rebranded derivative of GPLv3 OpenFOAM alongside it as HELYX-Core to paying customers. Presumably any customer who bought the software from them could redistribute the HELYX-Core component under GPLv3; but if it's basically just OpenFOAM and maybe a bunch of other OSS libraries bundled together, there would be little point in doing so. The added value would be in the GUI component, plus any add-ons and support services they provide. – Ilmari Karonen Jun 27 at 14:01
  • Considering the attention to the specific examples, I do add two external links involving discussions of this topic (one reply was from the Engys Manager): Engys proprietary or open source?, and How can HELYX-Core be based on OpenFOAM?. – Herpes Free Engineer Jun 28 at 7:52
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    @HerpesFreeEngineer having read those, I note with respect to your comment therein "GPLv3 completely forbids non-disclosure agreements" that GPLv3 s7 doesn't so much forbid them as give you clear permission to ignore them insofar as they purport to restrict your GPLv3 rights. – MadHatter Jun 28 at 8:40
  • I have added a correction to my remark thereat. That was a pretty amazing help from you. Many thanks. – Herpes Free Engineer Jun 28 at 9:34

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