docs/faq/legal.xml

<sect1 id="chapter-legal">
  <title id="title-legal">GStreamer Legal Issues</title>
  <para>
This part of the FAQ is based on a series of questions we asked the FSF
to understand how the GPL works and how patents affects the GPL. These
questions were answered by the <ulink url="http://www.fsf.org/">
FSF lawyers</ulink>, so we view them as the
final interpretation on how the GPL and LGPL interact with patents in our 
opinion. This consultancy was paid for by
<ulink url="http://www.fluendo.com/">Fluendo</ulink>
in order to obtain clear and quotable answers.  These answers were certified
by the FSF lawyer team and verified by FSF lawyer and law professor Eben Moglen.
  </para>

  <qandaset defaultlabel="qanda">

    <qandaentry>
      <question id="legal-distribute-three">
        <para>
Can someone distribute the combination of
<itemizedlist>
  <listitem><para>GStreamer, the LGPL library</para></listitem>
  <listitem><para>MyPlayer, a GPL playback application</para></listitem>
  <listitem><para>The binary-only Sorenson decoder</para></listitem>
</itemizedlist>
together in one distribution/operating system ? If not, what
needs to be changed to make this possible ?
        </para>
      </question>

      <answer>
        <para>
This would be a problem, because the GStreamer and MyPlayer licenses would
forbid it.  In order to link GStreamer to MyPlayer, you need to use section
3 of the LGPL to convert GStreamer to GPL.  The GPL version of GStreamer
forbids linking to the Sorenson decoder.  Anyway, the MyPlayer GPL
license forbids this.  
        </para>

        <para>
If the authors of MyPlayer want to permit this, we have an
exception for them: the controlled interface exception from the FAQ.
The idea of this is that you can't get around the GPL just by including
a LGPL bit in the middle.
        </para>

        <para>
Note: MyPlayer is a completely fictituous application at the time of writing.
        </para>

      </answer>
    </qandaentry>

    <qandaentry>
      <question id="legal-binary-plugin">
        <para>
Suppose Apple wants to write a binary-only proprietary 
plugin for GStreamer to decode Sorenson video, which will be shipped 
stand-alone, not part of a package like in the question above. 
Can Apple distribute this binary-only plugin ?
        </para>
      </question>

      <answer>
        <para>
Yes, modulo certain reverse engineering requirements in section 6 of
the LGPL.
        </para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question id="legal-gpl-program">
        <para>
If a program released under the GPL uses a library that 
is LGPL, and this library can dlopen plug-ins at runtime, what are the
requirements for the license of the plug-in ?
        </para>
      </question>

      <answer>
        <para>
You may not distribute the plug-in with the GPL application. 
Distributing the plug-in alone, with the knowledge that it will be used
primarily by GPL software is a bit of an edge case.  We will not advise you
that it would be safe to do so, but we also will not advise you that it
would be absolutely forbidden.
        </para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question id="legal-safe-countries">
        <para>
Can someone in a country that does not have software patents distribute 
code covered by US patents under the GPL to people in, for example, Norway ? 
If he/she visits the US, can he/she be arrested ?
        </para>
      </question>

      <answer>
        <para>
Yes, he can.
No,  there are no criminal penalties for patent infringement in the US.
        </para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question id="legal-unsafe-countries">
        <para>
Can someone from the US distribute software covered by
US patents under the GPL to people in Norway ? To people in the US ?
        </para>
      </question>

      <answer>
        <para>
This might infringe some patents, but the GPL would not forbid it 
absent some actual restriction, such as a court judgement or agreement.
The US government is empowered to refuse importation of patent
infringing devices, including software.
        </para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question id="legal-gpl-library-patents">
        <para>
There are a lot of GPL- or LGPL-licensed libraries that 
handle media codecs which have patents.  Take mad, an mp3 decoding library,
as an example.  It is licensed under the GPL. In countries where patents 
are valid, does this invalidate the GPL license for this project ?
        </para>
      </question>

      <answer>
        <para>
The mere existence of a patent which might read on the program does not
change anything. However, if a court judgement or other agreement
prevents you from distributing libmad under GPL terms, you can not
distribute it at all.
        </para>

        <para>
The GPL and LGPL say (sections 7 and 11):
<quote>If you cannot distribute so as to satisfy simultaneously your
obligations under this License and any other pertinent obligations, then
as a consequence you may not distribute the Library at all.</quote>
        </para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question id="legal-gpl-court-judgment">
        <para>
So let's say there is a court judgement. Does this mean that the GPL license is
invalid for the project everywhere, or only in the countries where it conflicts
with the applicable patents ?
        </para>
      </question>

      <answer>
        <para>
The GPL operates on a per-action, not per-program basis.  That is, if
you are in a country which has software patents, and a court tells you
that you cannot distribute (say) libmad in source code form, then you
cannot distribute libmad at all.  This doesn't affect anyone else.
        </para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question id="legal-gpl-and-binary">
        <para>
Patented decoding can be implemented in GStreamer either by
having a binary-only plugin do the decoding, or by writing a plugin
(with any applicable license) that links to a binary-only library.
Does this affect the licensing issues involved in regards to GPL/LGPL?
        </para>
      </question>

      <answer>
        <para>
No.
        </para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question id="legal-gpl-patent-distribution">
        <para>
Is it correct that you cannot distribute the GPL mad library to
decode mp3's, *even* in the case where you have obtained a valid license 
for decoding mp3 ?
        </para>
      </question>

      <answer>
        <para>
The only GPL-compatible patent licenses are those which are open to  
all parties posessing copies of GPL software which practices the 
teachings of the patent.
        </para>

        <para>
If you take a license which doesn't allow others to distribute
original or modified versions of libmad practicing the same patent
claims as the version you distribute, then you may not distribute at
all.
        </para>
      </answer>
    </qandaentry>
  </qandaset>
</sect1>