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

Måns Rullgård mru
Sat Jun 11 19:25:45 CEST 2005

Diego Biurrun <diego at biurrun.de> writes:

> On Sat, Jun 11, 2005 at 06:06:25PM +0200, M?ns Rullg?rd wrote:
>> That's a good example.  Now consider this: an application (A) uses a
>> GPL library (B), and, according to the FSF, is covered by the GPL.
>> Suppose that there exists a compatible library (C), under a
>> GPL-incompatible license.  By the same logic that made A a derivative
>> of B, it will now also be a derivative of C.
> False.  The logic that makes A a derivative of B is the fact that A
> _uses_ B, nothing else.

It will use whichever of B or C is found first by the dynamic linker.
The decision is made each time A is executed.

>> Hence, A must comply with the license requirements of both B and C.
>> These licenses being incompatible, such compliance is impossible,
>> rendering A undistributable.
> Nonsense.

Of course it is, which is why the "dynamic linking creates a derived
work" theory is false.

> A need not comply with the license requirements of C, unless it uses C.
> If it uses C it need not comply with the license requirements of B.

It can use B or C.  It's all up the dynamic linker on the machine
where A is run.  Hence, distributing A does not bind the distributor
to either of the licenses of B or C.

M?ns Rullg?rd
mru at inprovide.com

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