15

I publish photos under multiple Creative Commons licenses and often want to indicate the licensing in a short caption or comment on the photo online or in print. If one of them is dual licensed, how can I represent that in a way that will be recognized by as many people as possible?

My naive approach has been to simply concatenate the license names with || as a separator (example: CC-BY-SA || CC-BY-NC), which indicates a logical OR to me, but might mean nothing to non-programmers.

10

You're correct in your last paragraph at least: the || symbol will mean nothing to people who have no programming knowledge.

If you know that the only people visiting your project will be programmers, that's OK, but there are still less ambiguous ways to represent it.

In fact, the simplest way may be to simply say it:

This project is dual-licensed under <X> and <Y>.

For a short caption, you can simply shorten the text:

dual-licensed under <X> <Y>

And for a longer explanation, perhaps on the project website, you can expand it:

This project is dual-licensed, using licenses <X> and <Y>. You may choose to use either license when using any of this work.

(Substitute the second sentence for the relevant condition. If it's their option which license to use, tell them.)

  • I'd avoid the choice of words of "dual licensed" because it makes it sound like you might have to follow both, rather than being given a choice. So include the word "or" or "choice" or something like that, like the last suggestion. – curiousdannii Dec 24 '15 at 12:34
6

If you can spare words and it doesn't have to be language neutral, for example

You may use this work under the terms of either CC-BY-SA, or (at your option) CC-BY-NC

or

Your choice of CC-BY-SA or CC-BY-NC

The former is similar to what the GNU project uses in their GPL versioning to allow using the current or any later versions (http://www.gnu.org/licenses/gpl-3.0.html, under "How to Apply These Terms to Your New Programs"). The latter is by me, so use at your own risk.

3

It is usually sufficient to state that the project is dual licensed under two licenses and list them in the format of a list.

// This software (The source code, executables compiled from the
// source and attached documentation files within the repository)
// is dual licensed under:
// - The GNU General Public License (GPL) version 2.0; and
// - The Apache Software License (ASL) Version 2.0.
  • I'd avoid the choice of words of "dual licensed" because it makes it sound like you have to follow both, rather than being given a choice. – curiousdannii Dec 24 '15 at 12:28
  • @curiousdannii: I don't understand, how does the straightforward term lead to such implication? – Unihedron Dec 24 '15 at 12:30
  • 1
    Because for most people (and most people aren't very familiar with FLOSS and dual licensing) the wording isn't straightforward, and without explictly including the word "or" or "choice" or the like it would be perfectly understandable to think it means you have to follow both. – curiousdannii Dec 24 '15 at 12:33
3

What is the most concise unambiguous way to represent dual licensing of a work?

This would be using the SPDX "license expression" syntax as described in the SPDX 2.0 spec in "Appendix IV: SPDX License Expressions":

A common example is when software is offered under a choice of 
one or more licenses (e.g., GPL-2.0 OR BSD-3-Clause)

So I would use this way and ideally use this with SPDX license identifiers.

Disclaimer: I am one of the co-founders of SPDX.

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