[MPlayer-dev-eng] Re: help on libmpdemux usage (Modifié par Jérôme Cornet)

[Billy Biggs]

Jérôme Cornet (jerome at aldorande.net):

> [...]
> QuickTime IS a major component of MacOS X. You cannot install MacOS X
> without it. There are no possibilities to have a MacOS X system
> without QuickTime.  My codec is written for MacOS X, so it implicitly
> requires MacOS X which is not GPL the same way as Emacs for Windows
> implicitly requires ...er Windows! 
> [...]
> The guy was not talking about GPL's politics which is very good.
> Maybe i will ask the FSF about that matter, but to me the problem is
> that YOU don't want me to use MPlayer's parts in my GPL software.
> [...]

  Hi Jérôme,

  The discussion is less about how Richard Felker feels about his code
being used with Quicktime, and more about representing those who
released GPL'ed code which is included in mplayer.

  The GPL itself was written before plug-ins became a standard part of
software distribution, and before operating systems became the all-
encompasing systems that we see today.  Merging these two concepts
further complicates the problem, but we can try to decompose it.

  System libraries are those you cannot avoid using. For example, the
Win32 API and Sun's libc on a Solaris machine are clear examples of
system libraries.  However, while IE may be distributed with Windows,
most people would not consider it a system library, it is an
application.  Therefore, you cannot release a plugin for IE under the
GPL without an exemption.  For more on plug-ins, see:

  http://www.gnu.org/licenses/gpl-faq.html#GPLPluginsInNF

  Back to mplayer, libmpeg2 is an example of code included which is
GPL'ed without exemptions.  You therefore cannot use mplayer to write a
video loader for Matlab, even though your plug-in is completely
separate.  You can only write a GPL'ed Matlab application if you include
in your license a specific exemption.

  The Quicktime example is difficult.  Quicktime is a video framework,
basically equivalent to DirectShow under Windows.  An mplayer codec
would allow any Quicktime application to use mplayer for loading video
files (similar to ffdshow, except that ffmpeg is under the LGPL, making
this explicitly allowed).

  Even if we consider Quicktime a system library, if the intention is
for Quicktime Player to be able to decode AVI files using libmpdemux,
then clearly this is a violation of the GPL.  If the intention is for a
GPL'ed application which uses Quicktime to decode AVI files using
libmpdemux, then modifying that application to call libmpdemux would
make things much clearer.  Furthermore, since you could just mod the
app, then why is Quicktime is a system library?

  I hope this clarifies the debate a little.  There are very valid
reasons why the licensing issue is an important one, and why it's not an
easy one to answer.

  -Billy