Unclear license information regarding copyleft

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Unclear license information regarding copyleft

Sven Bartscher-2
Greetings,

(Please excuse if the below analysis is partly or even completely wrong,
reading about licensing and copyright issues often makes me quite confused)

I'm the maintainer of the package dwarf-fortress in non-free. The
package as a whole is clearly non-free as the license states that „you
may redistribute the *unmodified* binary and accompanying files“ and the
source code to the contained executable is not provided.

The package also contains a shared library called libgraphics.so and the
corresponding source code. The library links to (among others) SDL and
GTK which are licensed under the LGPL-2.1, AIUI this means that
libgraphics.so and its source code have to licensed under the LGPL. (due
to condition 2, correct?)

I could not find an explicit statement in the upstream tarball that
clarifies what license applies to the library in question. There is a
file called 'sdl license.txt' that contains a copy of the LGPL-2.1,
which hints that the author is aware that their work is in some way
affected by this license.

As there are some problems[1] with the compiled shared library as
distributed by upstream (and because compiling things ourselves is
always nicer) I would like to rebuild the library when building the
Debian package, though I'm not sure if it is clear in the given
situation that it is legal to recompile the library and distribute the
resulting shared library. But maybe someone smarter than me can
enlighten me.

[1]: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=898175

The files mentioned above can be found in the source package [2] at
these paths:
 * libgraphics.so: {amd64,i386}/libs/libgraphics.so
 * libgraphics.so source code: {amd64,i386}/g_src
 * sdl license: {amd64,i386}/sdl/sdl license.txt

[2]: https://salsa.debian.org/debian/dwarf-fortress

Regards
Sven


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Re: Unclear license information regarding copyleft

Simon McVittie-7
On Tue, 15 May 2018 at 19:22:54 +0200, Sven Bartscher wrote:

> I'm the maintainer of the package dwarf-fortress in non-free. The
> package as a whole is clearly non-free as the license states that „you
> may redistribute the *unmodified* binary and accompanying files“ and the
> source code to the contained executable is not provided.
>
> The package also contains a shared library called libgraphics.so and the
> corresponding source code. The library links to (among others) SDL and
> GTK which are licensed under the LGPL-2.1, AIUI this means that
> libgraphics.so and its source code have to licensed under the LGPL. (due
> to condition 2, correct?)

No. glibc is LGPL-licensed, the same as GTK[1], so if your interpretation
was correct, the dwarf-fortress developer would not be allowed to
distribute their proprietary executable that is linked to glibc.

The main difference between each version of the GPL and the corresponding
version of the LGPL is that you can link (possibly proprietary) objects
to a LGPL library without being obliged to release source for those
objects under the (L)GPL.

If the dwarf-fortress developer is the copyright holder of everything in
libgraphics, then the choice of license is up to them, as long as they
meet the conditions in LGPL-2.1 §6. They are under no obligation to
provide source code for it (under LGPL or otherwise), because LGPL-2.1
§5 and §6 apply to it.

> As there are some problems[1] with the compiled shared library as
> distributed by upstream (and because compiling things ourselves is
> always nicer) I would like to rebuild the library when building the
> Debian package, though I'm not sure if it is clear in the given
> situation that it is legal to recompile the library and distribute the
> resulting shared library.

The dwarf-fortress developer doesn't seem to have given you permission
to compile g_src into a replacement libgraphics.so and distribute the
result, so you can't; but it seems to be their intention that you can
(otherwise they wouldn't have released source code), so if you ask nicely,
it seems likely that they will give you that permission.

    smcv

[1] I don't know whether it's the same version of the LGPL, but the
    differences between versions are not particularly relevant here

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Re: Unclear license information regarding copyleft

Walter Landry-4
In reply to this post by Sven Bartscher-2
Sven Bartscher <[hidden email]> writes:

> Greetings,
>
> (Please excuse if the below analysis is partly or even completely wrong,
> reading about licensing and copyright issues often makes me quite confused)
>
> I'm the maintainer of the package dwarf-fortress in non-free. The
> package as a whole is clearly non-free as the license states that „you
> may redistribute the *unmodified* binary and accompanying files“ and the
> source code to the contained executable is not provided.
>
> The package also contains a shared library called libgraphics.so and the
> corresponding source code. The library links to (among others) SDL and
> GTK which are licensed under the LGPL-2.1, AIUI this means that
> libgraphics.so and its source code have to licensed under the LGPL. (due
> to condition 2, correct?)

As I understand it, libgraphics.so is not modifying SDL.  In general,
the LGPL only requires that you not get rid of the ability to
dynamically link in a new version of SDL.  So this is probably OK.

> I could not find an explicit statement in the upstream tarball that
> clarifies what license applies to the library in question. There is a
> file called 'sdl license.txt' that contains a copy of the LGPL-2.1,
> which hints that the author is aware that their work is in some way
> affected by this license.
>
> As there are some problems[1] with the compiled shared library as
> distributed by upstream (and because compiling things ourselves is
> always nicer) I would like to rebuild the library when building the
> Debian package, though I'm not sure if it is clear in the given
> situation that it is legal to recompile the library and distribute the
> resulting shared library. But maybe someone smarter than me can
> enlighten me.

I think you have to ask upstream about this (i.e. Tarn Adams).  Absent
any other information, I would think that you could not recompile the
source into a new binary.  It is probably just an oversight on the part
of the Dwarf Fortress developers.

I would phrase it as asking what license that part is under.  There are
a few obvious choices: LGPL 2.1 or later (to match SDL), MIT, or
Apache.  Please do not suggest a custom license.

Cheers,
Walter Landry

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Re: Unclear license information regarding copyleft

Sven Bartscher-3
Hi,

Am 15.05.2018 um 20:04 schrieb Walter Landry:

> Sven Bartscher <[hidden email]> writes:
>> As there are some problems[1] with the compiled shared library as
>> distributed by upstream (and because compiling things ourselves is
>> always nicer) I would like to rebuild the library when building the
>> Debian package, though I'm not sure if it is clear in the given
>> situation that it is legal to recompile the library and distribute the
>> resulting shared library. But maybe someone smarter than me can
>> enlighten me.
>
> I think you have to ask upstream about this (i.e. Tarn Adams).  Absent
> any other information, I would think that you could not recompile the
> source into a new binary.  It is probably just an oversight on the part
> of the Dwarf Fortress developers.
I already tried to do that, but haven't received an answer in 4 months.
Sorry, I forgot to mention that in my previous post.

> I would phrase it as asking what license that part is under.  There are
> a few obvious choices: LGPL 2.1 or later (to match SDL), MIT, or
> Apache.  Please do not suggest a custom license.

Regards
Sven


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Re: Unclear license information regarding copyleft

Sven Bartscher-3
In reply to this post by Walter Landry-4
Greetings,

Am 15.05.2018 um 20:04 schrieb Walter Landry:

> Sven Bartscher <[hidden email]> writes:
>> The package also contains a shared library called libgraphics.so and the
>> corresponding source code. The library links to (among others) SDL and
>> GTK which are licensed under the LGPL-2.1, AIUI this means that
>> libgraphics.so and its source code have to licensed under the LGPL. (due
>> to condition 2, correct?)
>
> As I understand it, libgraphics.so is not modifying SDL.  In general,
> the LGPL only requires that you not get rid of the ability to
> dynamically link in a new version of SDL.  So this is probably OK.
Ah, yes I was probably reading that wrong. Sections 5 and 6 seem to be
more relevant in this case. Thank you for pointing this out!

Regards
Sven


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Re: Unclear license information regarding copyleft

Walter Landry-4
In reply to this post by Sven Bartscher-3
Sven Bartscher <[hidden email]> writes:

> Hi,
>
> Am 15.05.2018 um 20:04 schrieb Walter Landry:
>> Sven Bartscher <[hidden email]> writes:
>>> As there are some problems[1] with the compiled shared library as
>>> distributed by upstream (and because compiling things ourselves is
>>> always nicer) I would like to rebuild the library when building the
>>> Debian package, though I'm not sure if it is clear in the given
>>> situation that it is legal to recompile the library and distribute the
>>> resulting shared library. But maybe someone smarter than me can
>>> enlighten me.
>>
>> I think you have to ask upstream about this (i.e. Tarn Adams).  Absent
>> any other information, I would think that you could not recompile the
>> source into a new binary.  It is probably just an oversight on the part
>> of the Dwarf Fortress developers.
>
> I already tried to do that, but haven't received an answer in 4 months.
> Sorry, I forgot to mention that in my previous post.

I think you have to bother them again.  Tarn Adams has probably
forgotten about your request.  You just have to be persistent.

Cheers,
Walter Landry

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Re: Unclear license information regarding copyleft

Sven Bartscher-3
Am 15.05.2018 um 20:45 schrieb Walter Landry:

> Sven Bartscher <[hidden email]> writes:
>> Hi,
>>
>> Am 15.05.2018 um 20:04 schrieb Walter Landry:
>>> Sven Bartscher <[hidden email]> writes:
>>>> As there are some problems[1] with the compiled shared library as
>>>> distributed by upstream (and because compiling things ourselves is
>>>> always nicer) I would like to rebuild the library when building the
>>>> Debian package, though I'm not sure if it is clear in the given
>>>> situation that it is legal to recompile the library and distribute the
>>>> resulting shared library. But maybe someone smarter than me can
>>>> enlighten me.
>>>
>>> I think you have to ask upstream about this (i.e. Tarn Adams).  Absent
>>> any other information, I would think that you could not recompile the
>>> source into a new binary.  It is probably just an oversight on the part
>>> of the Dwarf Fortress developers.
>>
>> I already tried to do that, but haven't received an answer in 4 months.
>> Sorry, I forgot to mention that in my previous post.
>
> I think you have to bother them again.  Tarn Adams has probably
> forgotten about your request.  You just have to be persistent.
Yes, I have sent three pings about this during those 4 months and I will
probably send a few more in the future if necessary. I was hoping we
could do something without a reaction from Tarn Adams, but I think there
was a bit too much wishful thinking from my side involved.

Of course this doesn't make the underlying copyright issue go away, so I
will just have to work around the library problems without modifying the
library.

Thank you for having looked into this!

Regards
Sven


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