[Ffmpeg-devel] Patch for dynamic liba52.so loading

August Mayer amayer
Sat Jun 11 17:26:11 CEST 2005

There is an advantage if it's possible to dynamically load liba52 (and 
libfaad). Say there is one commercial application (without source) that 
uses the dynamically-loaded libavcodec.so . There is a second GPL 
application that also uses libavcodec.so. Both applications could share 
the binary library (e.g. Debian package), legally. But only the GPL 
application would legally be allowed to use the AC-3 decoder.

I think the FSF explicitly states that GPL'ed dynamically-linked 
libraries do extend their copyright to the code they are linked to, even 
if this linking occurs at run-time ( 
http://www.gnu.org/licenses/gpl-faq.html#MereAggregation ). This, in 
reverse, is why it's somewhat of a dark-gray area to create binary 
closed-source Linux kernel modules. The Linux kernel is GPL, thus it 
extends this license to the loaded libraries. (However, "my home is my 
castle" and "Where no plaintiff, there no judge").

greetings    August

Rich Felker wrote:

>As long as the party setting it up for this use is not also
>distributing liba52 or outerwise doing something for it that requires
>accepting the GPL on liba52 I agree. On the other hand, if someone
>makes a proprietary program that needs to decode ac3, and distributes
>it with libavcodec compiled for dynamic liba52 loading, then offers a
>separate download of liba52 under GPL terms, they ARE infringing on
>liba52. Making them separate downloads or separating them in other
>ways does not get around the fact that they have prepared a non-GPL
>derivative work of liba52, thus invalidating their rights to
>distribute liba52 under the GPL.

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