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

[Måns Rullgård]

Rich Felker <dalias at aerifal.cx> writes:

>> > Of course there are multiple codec contexts. Is there a good reason
>> > for dynamic loading support? IMO it's unnecessary complexity that
>> > should just be removed..
>> 
>> There is no technical reason for dynamic loading.  It allows
>> libavcodec to be distributed under the LGPL, and still use liba52,
>> even if you believe the lies being perpetrated by the FSF.
>
> 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.

The point is that linking against liba52 (or any other library) does
not create a derived work.  There is a fair amount of evidence that
making use of a library through its API, does not amount to creating a
derived work.  The bits from the library that end up in the executable
linking to it (names of functions, mainly), are not subject to
copyright protection.  This is analogous to writing an article, in
which references to various books are made.  This does in no way
infringe on the copyright of the books referenced.

If APIs were protected by copyright, then creating a compatible
implementation would also be creating a derived work, and would
require proper permission from the copyright holder.  Creating a
compatible implementation is precisely what the FSF has done in the
case of the OpenSSL compatibility layer of GnuTLS.  If the FSF
requires users of the APIs of their libraries to allow the GPL to
extend the using application, then how can they consider themselves
having the right to duplicate the interfaces of others?

If you want more details on the topic, read the debian-legal archives.

-- 
M?ns Rullg?rd
mru at inprovide.com