[Libav-user] Getting to grips with ffmpeg

John Dexter jdxsolutions at gmail.com
Mon Feb 6 15:02:01 CET 2012

On 6 February 2012 09:32, Nicolas George <nicolas.george at normalesup.org> wrote:
> 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.

Thanks Nicholas and Phil... obviously I have no problem providing
source if asked to, and in putting the license in my redistributable.
I read somewhere that including a link to where users could download
the source themselves can be counted as "distributing the source"?
I was very surprised by claims it's a requirement, simply because none
of the LGPL libraries I've used have ever mentioned it in the case of
dynamic linking.
I found this discussion: http://teem.sourceforge.net/lgpl.html -
search for "the interesting part". Obviously only one person's view of
it, but it seemed to make sense.

Thanks again.

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