Can I license artwork that has a mixture of CC BY-SA, public domain, CC0, Pexels licensed images under CC BY-SA?

Question

I have created some artwork that uses images mostly licensed under variations of CC BY-SA. There are also some public domain, CC0, and rarely images from Pexels/similar "free to use" sites. Since I believe the CC BY-SA license requires me to license my derivatives/modifications under the same license as the original, I was planning on using the CC BY-SA 4.0 license for all of my artwork. As I started attributing my work it got me thinking; I may have read somewhere that since a CC0 (and possibly public domain) work waives all rights, I cannot do anything to restrict another person's usage of that image. Would applying a CC BY-SA license to work that includes a mixture of images with a mixture of previously mentioned licenses (or lack of license) constitute as restricting another person's usage of these images, or since my work includes creative modifications am I fine to license everything under CC BY-SA?

Answer 1

No to the Pexels question; reading their license, there are a bunch of things here which are incompatible with all open source licenses, whether CC BY-SA or anything else:

• "Identifiable people may not appear in a bad light or in a way that is offensive.": an open source license must allow me to use a work in any way, even ones which offend people.
  • You can obviously ignore this problem if none of the images you obtain from Pexels include identifiable people.
• "Don't sell unaltered copies of a photo or video, e.g. as a poster, print or on a physical product without modifying it first.": we have a canonical question on this
  • Although you can comply with the letter of the license if before including the image you modify the shade of one pixel by 1/256 (or less if it has more than 8 bit data) in either red, green or blue; it is then a modified image.
• "Don't redistribute or sell the photos and videos on other stock photo or wallpaper platforms.": as for the previous point, but there's no way round this one.
  • From a legal point of view, this clause worries me generally. Who defines what is a "wallpaper platform"?

The other licenses are okay - public domain images you can do what you like with, and CC0 is essentially just a dedication to the public domain on a slightly firmer legal footing.

Answer 2

I may have read somewhere that since a CC0 (and possibly public domain) work waives all rights, I cannot do anything to restrict another person's usage of that image.

If you take an image that is under CC0 or public domain and make changes to it, then you can use any license you like for your modified image, including one that forbids all further modification.

What you cannot do is forbid someone to also fetch the original image and start making changes to that.

Would applying a CC BY-SA license to work that includes a mixture of images with a mixture of previously mentioned licenses (or lack of license) constitute as restricting another person's usage of these images, or since my work includes creative modifications am I fine to license everything under CC BY-SA?

Applying the CC BY-SA license would not constitute a forbidden restriction on another person using those images.

On the other hand, I am also not fully confident you can license everything under CC BY-SA.

The problematic license here is the Pexels license. That is a non-free license that has some restrictions on how you can use the images. It is unclear to me to which extent the restrictions of the Pexels license need to remain in force in a derived work and they are not part of the CC BY-SA license.

Answer 3

• You can apply the CC BY-SA 4.0 license to your modifications of the original works (including CC BY-SA licensed works).
• You cannot impose restrictions (like attribution or ShareAlike) on works that are under CC0 or Public Domain, because those works are no longer under copyright and cannot be restricted.
• Just be clear in your attribution that some parts of your work are licensed under CC0 or are in the Public Domain, and others are licensed under CC BY-SA 4.0.

So, yes, you can license your derivative work under CC BY-SA, but you must acknowledge the differences between the various elements used (e.g., CC0 and Public Domain content) and apply the correct attribution rules accordingly.