Licence to prevent sharing a modified copy of a software?

Question

Is there any open source licence that would allow one individual to copy, modify, share the source code of the project while preventing to share a modified copy of the project?

I'm asking that thinking about security softwares that are closed-source because of the need of 'making money' in the business model.

This trick could allow one company to have an open source software including some kind of token verification or anything else that requires a payment for the use of the software. While this can sound fuzzy because one individual could easily take the source code and modify it so as to use the software free of charge, the majority of people who don't have the skills to do so would pay for it.

While I understand this can go against the free in the sense of liberty and free of charge I do really think it could be useful.

Answer 1

No.

Any open source license allows anyone to share modified source code.

From the annotated open source definition clause 3:

3. Derived Works

The license must allow modifications and derived works, and must allow them to be distributed under the same terms as the license of the original software.

Rationale: The mere ability to read source isn't enough to support independent peer review and rapid evolutionary selection. For rapid evolution to happen, people need to be able to experiment with and redistribute modifications.

Answer 2

Wikipedia has quite a good section on this topic:

Although the OSI definition of "open source software" is widely accepted, a small number of people and organizations use the term to refer to software where the source is available for viewing, but which may not legally be modified or redistributed. Such software is more often referred to as source-available, or as shared source, a term coined by Microsoft in 2001. While in 2007 two shared source licenses were certified by the OSI, most of the shared source licenses are still source-available only.

In 2007 Michael Tiemann, president of OSI, had criticized companies such as SugarCRM for promoting their software as "open source" when in fact it did not have an OSI-approved license. In SugarCRM's case, it was because the software is so-called "badgeware" since it specified a "badge" that must be displayed in the user interface (SugarCRM has since switched to GPLv3). Another example was Scilab prior to version 5, which called itself "the open source platform for numerical computation" but had a license that forbade commercial redistribution of modified versions. Because OSI does not have a registered trademark for the term "open source", its legal ability to prevent such usage of the term is limited, but Tiemann advocates using public opinion from OSI, customers, and community members to pressure such organizations to change their license or to use a different term. Although the OSI definition of "open source software" is widely accepted, a small number of people and organizations use the term to refer to software where the source is available for viewing, but which may not legally be modified or redistributed. Such software is more often referred to as source-available, or as shared source, a term coined by Microsoft in 2001. While in 2007 two shared source licenses were certified by the OSI, most of the shared source licenses are still source-available only.

So it boils down to the fact that quite a lot of companies have actually done the thing you were wondering about and whether the term open source may be used to describe this behavior has been debated quite a lot and taking a position one way or another would make for an incomplete answer. The simple reality is that open in open source can both mean openly available and free to be changed depending on the context of where and with whom the term is used. In the source code world there is a whole range from 'public domain' down to 'closed source' and the best thing to realize is that it's best to just judge each license on its own merits.

The important thing however is that there definitely are licenses that allow you to do exactly what you want to do, regardless of how they are called. There are however no freely-usable licenses of such type that I know of, as a license - just like any intellectual work- is by default copyrighted, so companies tend to just write their own license when they wish to make their source code view-able.

Answer 3

The open source definition explicitly allows the license to forbid distributing modified versions under the same name, originally to accomodate TeX's requirement that modified versions can't be called TeX, but also for cases like the one described (i.e., some version is, say, certified, any modification would led to losing the certified status).

Please check the standard OSI-approved licenses (or the FSF-approved ones). But please stay GPL-compatible as far as possible. License proliferation could lead to forbidding useful combinations, loss for us all.