I was reading around the topic of the precise details of subscriber-content licensing on SE, and I found (and read more carefully than the previous times I'd seen it) this thread on FOSS.SE from 2017, which points out that content on Stack Exchange is actually dual-licensed.
The current Terms of Service, immediately after requiring users to agree to license their content under CC BY-SA, go on to require that
you grant Stack Overflow the perpetual and irrevocable right and license to access, use, process, copy, distribute, export, display and to commercially exploit such Subscriber Content [...] as reasonably necessary,
i.e., the ToS explicitly carves out a second license allowing SE to distribute the subscriber content even if their Creative Commons license expires. This can happen e.g. if the subscriber content was provided under CC BY-SA 3.0 and SE breaks the terms of the license, such as by distributing content under a license that's incompatible with CC BY-SA 3.0, such as the 4.0 version of the license. In this sense, it's useful that SE can continue to distribute the content, but the illegal change diminished the protections to the content instead of increasing them: while SE can distribute content, users cannot redistribute it, since the CC BY-SA 3.0 license that SE originally held to distribute it has been automatically revoked.
However: this does not seem to be the case for content contributed before 1 May 2018, as pointed out in the FOSS.SE thread linked above: in the Terms of Service active until May 2018, the equivalent section reads
You grant Stack Exchange the perpetual and irrevocable right and license to use, copy, cache, publish, display, distribute, modify, create derivative works and store such Subscriber Content and, except as otherwise set forth herein, to allow others to do so in any medium now known or hereinafter developed (“Content License”) in order to provide the Services, even if such Subscriber Content has been contributed and subsequently removed by You.
What is the precise status of this clause?
- Does it permit Stack Exchange to allow others to distribute and modify the content outside of the boxes drawn up by the Creative Commons Attribution-ShareAlike license?
- Or is this simply an (ultimately unnecessary) precision on the details of what the preceding sentence, which specifies the CC BY-SA license, entails?
Can we ask a Stack Overflow member to clarify once and for all what is the status of this language? Do the Terms of Service specify a dual license to the content? If so, what are the limits to the secondary license, and how do they extend to third parties? Or does Stack Overflow see its rights to the content as specified only by the relevant Creative Commons license?
Similarly, since May 2020, this section of the ToS reads
You agree that any and all content [...] is perpetually and irrevocably licensed to Stack Overflow on a worldwide, royalty-free, non-exclusive basis pursuant to Creative Commons licensing terms (CC BY-SA 4.0), and you grant Stack Overflow the perpetual and irrevocable right and license to access, use, process, copy, distribute, export, display and to commercially exploit such Subscriber Content, even if such Subscriber Content has been contributed and subsequently removed by you as reasonably necessary to, for example (without limitation):
- Provide, maintain, and update the public Network
- Process lawful requests from law enforcement agencies and government agencies
- Prevent and address security incidents and data security features, support features, and to provide technical assistance as it may be required
- Aggregate data to provide product optimization
This means that you cannot revoke permission for Stack Overflow to publish, distribute, store and use such content and to allow others to have derivative rights to publish, distribute, store and use such content. The CC BY-SA 4.0 license terms are explained in further detail by Creative Commons, and the license terms applicable to content are explained in further detail here.
so again this seems to be detailing a dual license, but maybe this is just a convoluted (and ultimately unnecessary) way of explaining the effects of the CC BY-SA 4.0 license, and it includes several cases of broad and unclear language (most notably, what does "provide the public Network" mean? Is that just business-as-usual display of subscriber content?).
So as things stand, several aspects still need explicit confirmation from SE staff.
- Does the new language still imply a dual license? Did it imply a dual license in the previous versions?
- Under which versions of the ToS does the second license allow SE to allow for redistribution?