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Re: Unsplash, the DFSG, and the GPL

From Sebastian Crane@21:1/5 to All on Fri Mar 14 15:40:01 2025

Dear ziproot,

Really interesting questions and about a wonderful game too! I'll do my best to answer.

CC-BY-SA 3.0 and CC-BY-SA 4.0 are known as 'GPL-compatible' because they don't add additional restrictions on the end user. It is fine to include them with a GPLv3 piece of software and they are allowed in Debian.

The Unsplash License appears not to be allowed in Debian ("License must not be specific to Debian" in the Debian Free Software Guidelines), because it does not allow the use of the copyrighted work in any way that competes with Unsplash. I believe that,
unfortunately, these specific game assets can not be distributed by Debian and would have to be replaced with free and open source alternatives.

Including AppImage binaries that are themselves made from FOSS isn't a problem for the GPL, and you can also often include proprietary binaries alongside the GPL with the 'mere aggregation' principle that you mention. The bigger issue is that Debian
tries to build everything from source - I think you'd need to be generating the AppImage from source in your own build scripts to be accepted into Debian.

You mention the non-free and contrib sections. Technically, these are not part of Debian. I don't have any first-hand knowledge of these so I'll defer to someone more experienced to answer your questions about those!

Best wishes,

Sebastian

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From Soren Stoutner@21:1/5 to All on Fri Mar 14 12:10:45 2025

Copy: [email protected] (ziproot)

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On Thursday, March 13, 2025 10:33:25 PM Mountain Standard Time ziproot wrote:

Hello all,

I am ziproot, a contributor to the video game Endless Sky, which has been on Debian repos in the past. I have a few questions concerning copyright.

1. Endless Sky’s source code is licensed under the GNU General Public License
v3 or later, however, there are images licensed under CC-BY-SA 3.0, CC-BY-SA 4.0, and the Unsplash License. Is this a violation of the GPL?

The CC-BY-SA 4.0 is not a problem for the GPL-3, but it isn’t compatible with the GPL-3+.

https://www.gnu.org/licenses/license-list.html#ccbysa

The CC-BY-SA 3.0 is not compatible with the GPL.

https://creativecommons.org/share-your-work/licensing-considerations/compatible-licenses/

The Unsplash License is not DFSG-free, and is not compatible with the GPL. This is due to
the last line in the license.

"This license does not include the right to compile images from Unsplash to replicate a
similar or competing service."

a. There are some binaries, such as an AppImage, which are packaged with the compiled source code and all of the images. Would this violate the GPL, or is this considered an aggregate? If this does violate the GPL, what would be necessary to make it GPL compliant? In other words, what images would need to be removed, or if possible, what would be necessary to include both the assets
and the source code as licensed?

As Sebastian explained in a separate email, this isn’t a problem for the GPL as long as the
source code is available that is used to create the binaries. For Debian, if the binaries need
to be a part of the Debian package, they should be compiled at build-time from the source
code.

2. Are these licenses allowed in Debian repos? If not, which ones are not, and
would it be possible to include Endless Sky in the contrib and/or non-free repos instead?

If you are unfamiliar with the Unsplash License, its terms are here: https:// unsplash.com/license/

All of the licenses except Unsplash are DFSG-free, so they are allowed in the main
repository (note that individual packages must use compatible licenses as described
above).

Unsplash is not DFSG-free, so if you wanted to ship a package using it, it would have to
ship in non-free. (As an explanation, everything in main is DFSG-free. Things in non-free
are not DFSG-free in some way, but do grant distribution permissions. Things in contrib
are DFSG-free but depend on a package in non-free.)

However, as you can’t combine Unsplash or CC-BY-SA 3.0 code with the GPL, there is no
way you can ship Endless Sky in its current state in Debian or anywhere else.

If you wish to view the game's repository for more information, you can do so here: https://github.com/endless-sky/endless-sky/

Thank you for your support.

I hope this is helpful. I wish you luck sorting out the licensing problems upstream. My
personal experience is that many upstream projects are not very careful about combining
licenses that aren’t actually compatible. Often, it is when a Debian package is being
prepared that they are alerted to the fact that they have been shipping incompatible code
for years. Sometimes this is easy to fix upstream and sometimes it takes a lot of work to
excise the incompatible licenses.

--
Soren Stoutner
[email protected]

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<body>On Thursday, March 13, 2025 10:33:25 PM Mountain Standard Time ziproot wrote:
> Hello all,
> > I am ziproot, a contributor to the video game Endless Sky, which has been on
> Debian repos in the past. I have a few questions concerning copyright.
> <p style="margin-top:0;margin-bottom:0;margin-le

From Soren Stoutner@21:1/5 to All on Sat Mar 15 16:20:28 2025

Copy: [email protected] (ziproot)

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On Friday, March 14, 2025 12:10:45 PM Mountain Standard Time Soren Stoutner wrote:

However, as you can’t combine Unsplash or CC-BY-SA 3.0 code with the GPL, there is no way you can ship Endless Sky in its current state in Debian or anywhere else.

I realized that when I wrote this I made an assumption that might not be true. You cannot
combine GPL and CC-BY-SA 3.0 code into a single binary or a linked library. So, if any of
the files that are licensed under the GPL are compiled or linked as shared libraries against
any of the files licensed under the CC-BY-SA 3.0 you are not compliant with the licenses.

However, if the files under these two licenses are completely separate than it isn’t an issue.
For example, if the code is all under the GPL and some of the graphic files are under the
CC-BY-SA 3.0, and if those graphic files are shipped as, for example, separate .png files
that are loaded by the binaries at runtime, then this would not be a problem.

I haven’t looked at the code for Endless Sky, but I realized that as it is a game this might be
what it is doing.

Of course, nothing about this changes what I wrote about Unsplash being DFSG-non-free.

--
Soren Stoutner
[email protected]

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<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
</head>
<body>On Friday, March 14, 2025 12:10:45 PM Mountain Standard Time Soren Stoutner wrote:
> However, as you can’t combine Unsplash or CC-BY-SA 3.0 code with the GPL,
> there is no way you can ship Endless Sky in its current state in Debian or
> anywhere else.
 I realized that when I wrote this I made an assumption that might not be true.  You cannot combine GPL and CC-BY-SA 3

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Re: Unsplash, the DFSG, and the GPL

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