[Libav-user] Getting to grips with ffmpeg

Nicolas George nicolas.george at normalesup.org
Mon Feb 6 10:31:49 CET 2012

L'octidi 18 pluviôse, an CCXX, John Dexter a écrit :
> If you're going to make such assertions please back them up. My
> research into dynamic linking of (L)GPL libraries finds multiple
> explicit claims that distribution of the library source code is _not_
> required if I haven't modified the original, according to LGPL section
> 6, specifically 6b.
> (http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html linked from
> ffmpeg legal page).

As pointed out by someone else, 6b covers the case where you do not
distribute the library at all, you distribute only the application, and rely
on the user to provide a suitable version of the library, probably by
already having it on their system.

Theoretically, the (L)GPL requires you to distribute the source code, even
if it was just compiled and not modified. A lot of projects will not take it
amiss if you do not distribute unmodified sources, provided you meet the
other requirements, especially the prominent notice. In other words, they
are interested in your enhancements to the code, not in hogging your
bandwidth. People in ffmpeg are more strict about the requirements because
there have been problems in the past.

Please also note that 6c is more risky than it appears, and more risky than
6a: with 6a, you only need to provide the source code to the people you
distributed the product, that is just a few megabytes in one corner on your
installation medium. With 6c, you must provide the source code to whoever
asks, because the offer can be transmitted from one person to another,
outside your control.


  Nicolas George

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