Can I use source code licensed under CC-BY-SA for commercial closed source project?

Question

I want to use some source code under CC-BY-SA for my company's project. That project is commercial and closed source code. I want our project not to have obligation to release the source code. Is this possible?

Answer 1

You can include CC-BY-SA source code in proprietary software iff you do not publish that software. The CC-BY-SA requirements only apply once you Share^[1] the adapted work. For example, this would allow internal tools, or possibly a server backend where that usage does not constitute a public performance.

^{[1] as defined in section 1.k in the CC-BY-SA 4.0, compare Distribute and Publicly Perform in sections 1.d and 1.j in the CC-BY-SA 3.0}

If you desire to publish software that was adapted from CC-BY-SA source code, you can only do so under the terms of that license. In particular:

• you must publish your software under that version of the CC-BY-SA or a compatible license,
• you must provide proper attribution for the original source code,
• you must not apply additional terms or restrictions, and
• you must not apply technical restrictions such as DRM.

Note that these requirements may be at odds with the terms and conditions of some app stores.

Absent from the CC-BY-SA is the requirement to publish your source code. You can publish CC-BY-SA software in any format you like, including in compiled form. However, recipients of that software are free to reverse-engineer and decompile it, and to adapt that software. So while the CC-BY-SA is generally similar to the GPL, the CC-BY-SA does not require you to publish your preferred form of making modifications (the source code).

Note that most code on Stack Overflow is licensed under the CC-BY-SA 3.0. This means that such code cannot be copied freely, not even for open-source projects, unless they are licensed under a CC-BY-SA 3.0 compatible license (which, indirectly, includes the GPLv3).

Answer 2

The conditions for CC-BY-SA in the current version 4.0 (but 3.0 is the same) are specified on https://creativecommons.org/licenses/by-sa/4.0/ . They state:

If you [...] build upon the material, you must distribute your contributions under the same license as the original.

The complicated term here is "contribution". If you have a 200,000 lines commercial project and you include a 2,000 line CC-BY-SA library into it, is your big commercial project a contribution to that library? Well, I would say "no", and I go so far to say, that most people, including most lawyers and most judges, would answer "no" to that question.

A contribution is usually something, that people give with the intention to give and to improve a bigger piece of work. Both of that is not true for your library inside your bigger work. Yes, the 2,000 line CC-BY-SA library included in your 200,000 line work would clearly be a contribution to that work, but not the other way round. Your big work will in most cases not be considered a contribution to that library.

If you have a house and then you build a city, you would say, that the house contributed to the city, but you would not say, that the city contributed to the house.

Of course, if in the process of creating your work, you also improve on the library itself, that would usually be considered a contribution to the library. And then, you have to publish the improved library, even, if you use the whole work only for yourself, because you have build upon the library. Unlike LGPL, where you only need to publish source code of improved libraries, once you distribute a work containing that library, CC-BY-SA forces you to publish those works, that you contributed to, once you build anything (useful) out of them.