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Sarah Gooding

13 Sources For Free Public Domain and CC0-Licensed Images

Yesterday, we featured WP Inject, a plugin that makes it easy to insert Creative Commons licensed images into WordPress content. High quality CC-licensed images are incredibly easy to find these days. The vast majority of the collections include images that fall under the Creative Commons Attribution-Sharealike 2.0 license. While these images are fine for blogging, they cannot be distributed with GPL-licensed software.

Why Creative Commons 2.0 Is Not Compatible With the GPL

When I submitted my first theme to the WordPress Themes Directory, I learned that most CC-licensed images are not compatible with the GPL. At first it seemed odd to me that they wouldn’t be compatible, given that they both offer so much freedom.

Samuel “Otto” Wood explained why certain Creative Commons licenses are not compatible in an answer on the WordPress.org support forums:

Because CC-BY-SA cannot be sublicensed, then that means it cannot be distributed in a work under the terms of the GPL. So it cannot be included in a GPL-compatible work-as-a-whole.

If you want to include images in a GPL-licensed work, you’ll need to select from those that fall under a compatible license.

According to the GNU licensing classifications, CC0 is the only Creative Commons license that is compatible with the GPL:

CC0 is a public domain dedication from Creative Commons. A work released under CC0 is dedicated to the public domain to the fullest extent permitted by law. If that is not possible for any reason, CC0 also provides a lax, permissive license as a fallback. Both public domain works and the lax license provided by CC0 are compatible with the GNU GPL.

If you are distributing a GPL-licensed product with images, such as a WordPress theme or plugin, your best bet is to opt for using images with the CC0 or Public Domain license.

13 High Quality Sources for CC0 and Public Domain Licensed Images

CC0 and Public Domain licensed images are not as easy to find as those that fall under the CC 2.0 license. Nevertheless, I was able to locate 13 high quality sources for finding images that are suitable for inclusion in GPL-licensed works. All of the following sites explicitly state a Public Domain or CC0 license for the images collected.

Unsplash

unsplash

PublicDomainPictures

publicdomainpictures

Pixabay

pixabay

SplitShire

SplitShire

1 Million Free Pictures

1millionfreepictures

Viintage

vintage

Gratisography

gratisography

Little Visuals

littlevisuals

PDpics

pdpics

The British Library

britishlibrary

New Old Stock

nos

Pickup Image

-A-lake-near-the-base-of-Copahue-volcano-031214D6BC845BA9

Public Domain Archive

publicdomainarchive

You’ll want to bookmark these sites for the next time you’re building a WordPress theme or plugin for distribution on WordPress.org. Do you have any other favorites to recommend? Please share them in the comments.

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21 responses to “13 Sources For Free Public Domain and CC0-Licensed Images”

  3. Great post Sarah!

    Excellent idea to mix the educational content on licensing and a explanation of CC & GPL compatibility with the list of sites that offer a solution. Now when I can’t find what I need on Unsplash, I know where to come to find alternatives.

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    • Wow! Picjumbo is awesome, thanks for the heads up on that @satrya. Do you know if the images on Picjumbo are CC0? It’s not very straightforward on his site and I emailed him and he didn’t give me a clear answer on the exact licensing. Here was his response:

      “Thanks Matt! There is no licence, check out Terms & FAQ in the left menu :)
      Cheers!
      Viktor Hanáček”

      I want to use some of these images but only if they are CC0. Would you think that his reply means they are CC0?
      Thanks,
      Matt

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  5. When I’m a little too tired to meet a decent creative bar, I often go ‘cruising for images’. Mostly for content, though, rather than licensed software.

    It’s good to see the warning, that many free resources are not going to be ‘free enough’ for inclusion in GPL software.

    I have come across arguments or insinuations that the GPL should be ‘softened’, or that it’s criteria ought to be reexamined … and I must say, this form of activism might at times be behind some offers of “free” materials. Trying to ‘pry’ the GPL off it’s strong stance…

    Not everyone likes the GPL … but an element of self-interest is always hiding in the small-print. Do all the homework; don’t grab-and-run.

    Incidentally, out-of-copyright old books are fabulous … but again, investigate the Terms of image-providers assiduously.

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  6. Thanks for all these great resources Sarah! I’m a little confused on the CC licenses though. It seems like you *skipped* from Public Domain to CC Share Alike. Isn’t “CC-Attribution” *in-between* (permissions wise) those 2 choices?

    I was once told by a CC person that you never really needed to make work PD, because CCA afforded all the same permissions and flexibility. He also made the point that a lot of people like the “sound” of CC-Share Alike, since it seems like “keep free culture free” but that Share Alike actually introduces a “viral component” that can create future incompatibilities, exactly as you’ve described.

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  12. I think there is something not quite right in his answer. This is what he really says:

    “I figured I’d go ahead and give an exact answer to this, despite all the talk-talk above about it.

    The CC-BY-SA 3.0 Unported license is incompatible with the GPL for one simple and specific reason.

    “You may not sublicense the Work.”

    Any given “work” rests under a license. The license is your terms by which the work-as-a-whole may be used/distributed/etc.

    In our repository, we require that the license for the work-as-a-whole be compatible with the GPL. This includes *everything* in the theme. CSS, images, everything. The whole ZIP of the theme must be GPL-compatible, and by extension, everything in there must be GPL-compatible. This is *our* restriction, we want it this way. WordPress itself is free-as-in-speech and we want to ensure that everything hosted else here on WordPress.org is just as free, to everybody, forever.

    So, because CC-BY-SA cannot be sublicensed, then that means it cannot be distributed in a work under the terms of the GPL. So it cannot be included in a GPL-compatible work-as-a-whole. So we don’t allow it here. This is actually for your protection, as an author. If you were to include CC-BY-SA images in your theme, and then say your theme is distributed under the terms of the GPL, then *you* are actually breaking *their* license. And because we’re hosting it, then so are we, by accident. Now, it’s not likely to cause any stir or ruckus or anything, but if we want people to respect our licensing conditions, then it’s only fair that we respect everybody else’s licensing conditions as well. Therefore our rules about GPL-compatibility are hard, fast, and unbreakable, period. Doesn’t matter how “free” you think the license is, if it’s not GPL-compatible, then it can not be on this site.”

    The error he makes here, and which he actually unjustly perpetuates, is equalling ‘being compatibel with GPL’ with ‘being GPL’. Let me explain. He begins with asserting that the CC-BY-SA isn’t compatible with the GPL. The given reason is: ‘because it can’t be sublicensed’. But…neither can the GPL. You can’t just take a work under the GPL, and then use it later on and claim it’s under another licence. So, in this regard, it’s EXACTLY the same. This means, the CC licence IS compatible with the GPL: if both are incorporated, then both can exist side by side, and one doesn’t contradict the other.

    The real and actual problem is not that they aren’t compatible, but that WordPress requires everything BEING GPL. This is the crux of the matter. You can’t just change a CC (except CC0) work into something else as a licence, and you can’t change a GPL licensed work into something else as licence. Therefore, if you ONLY accept a GPL licence, as wordpress does, then you’ve got a problem. Both licences are compatible with eachother, it’s the strict insistence that only one licence can be used that makes this an issue.

    For instance, if you took *the exact* same rules and terms of the GPL, yet called it differently, and gave it another name, say ‘LPG’… then still wordpress would say it can’t be used (and wrongly claim it’s not compatible), because that licence can’t be changed into GPL. Even though it is exactly the same, content wise.

    The solution is rather straightforward. If WordPress decides today that CC1 can be used as well (seen the fact that it boils down to the same), then it would immediately become ‘compatible’ as well. There is nothing in the ‘you can’t distribute it under another licence’ that ain’t there in the GPL too, after all. Thus, it doesn’t give any MORE restrictions then the GPL, only it does it with another licence in its name.

    I therefore think it is a bit misleading and FUD to claim CC-BY-SA isn’t compatible with GPL. It is. The best example can be seen on wikipedia: there the GPL is used too, yet they’re happy to incorporate that CC licence as well (as pictures, for instance). They don’t deem it ‘incompatible’ at all – or they would have removed it a long time ago. The reason is simple: they allow different licences, as long as they all provide the same kind of protection/free use. The licence itself is compatible, it’s the insistence no other licence can be used that makes the two incompatible.

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  15. I have a question about these sites Sarah!
    I’m a writer on a site called WattPad, maybe you have heard of it?
    Anyway, I need photos so as to make my book covers and I have literally been going crazy looking for copyright-free images and found none until today, so thank you!
    Now, my question is will I be able to use photos from these sites mentioned above to make my book covers without breaking copyright law?
    I’m not publishing my books, but when I do of course I won’t use these, my point is I want to make absolute sure I won’t get in trouble since I do have to modify the pictures for my book covers.
    Any ideas? Would appreciate the help!

    * lone author*

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  16. I’ve sent an email to the folks at Public Domain Pictures http://www.publicdomainpictures.net/ because they seem to be conflicted in their own distribution of images. I found a nice pic I wanted to redistribute but found the follow, seemingly contradictory, text:

    “License: Public Domain [http://creativecommons.org/publicdomain/zero/1.0/]. If you are going to redistribute this image online, a hyperlink to this particular page is mandatory.”

    Seems to me they don’t actually understand what “Public Domain” really means…

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