[FFmpeg-devel] [RFC] libfdk_aac license

[Jan Ekström]

On Sat, Jun 9, 2018 at 11:00 PM, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
> 2018-05-29 6:53 GMT+02:00, Gyan Doshi <gyandoshi at gmail.com>:
>>
>> On 29-05-2018 03:34 AM, Carl Eugen Hoyos wrote:
>>
>>> Just remove "and is not known...",
>
>>> please don't state that you guarantee
>>> they are compatible.
>
> Where should we sent people who trust what you wrote in the
> documentation but had to find out it isn't correct?
>
>> If we are continuing to permit LGPL compilation, shouldn't it be
>>
>> "The Fraunhofer AAC library is licensed under a license incompatible
>>   to the GPL. Therefore, for GPL builds, you have to pass
>>   @code{--enable-nonfree} to configure to use it.
>
>> To the best of our knowledge, it is compatible with the LGPL" ?
>
> I am curious because of your follow-up in another thread:
> Why do you think it is compatible?
>
> Carl Eugen

IANAL, but here goes:

I think the general idea was that since LGPL lets you link an LGPL
library in a proprietary piece of software (given that you follow the
spirit and language of LGPL by letting people build the same version
and making it possible for the built version to be loaded up in the
proprietary application), it probably works the other way as well. If
you have a proprietary module that you have provided the necessary
means to link against, an LGPL piece of software can utilize that as
long as the LGPL part of the deal is kept. Of course the means to
build this mish-mash is also to be provided to the user. I think
VideoLAN's or FSF's or so lawyers looked into this before, although I
might be incorrect. That is why non-free libraries tend to only be
requiring a special flag that makes the result non-distributable if
you don't enable GPL modules.

Of course, the requirement for fdk-aac has lessened after the internal
AAC encoder improved, but I still think some people are into it for
one reason or another. Too bad its license is just incompatible with
GPL (unless you remove all of the currently-still-patented stuff, I
guess, since the license's "additional restraints" were dealing with
patents. Which was the reading of the Red Hat lawyers - although I'm
not sure what if anything at all they're linking against it in
Fedora).

Best regards,
Jan