[Libav-user] Licensing question

Alex Cohn alexcohn at netvision.net.il
Fri Dec 13 21:34:32 CET 2013

On Wed, Dec 11, 2013 at 6:08 PM, Ioan Stan <Ioan.Stan at accesa.eu> wrote:
> Let’s suppose that I own a library named "a.dll" that is linked statically or dynamically with FFmpeg library. Another library owned by me and named "b.dll" is linked dynamically with "a.dll". A plug-in based application owned by me and named "App.exe" uses "b.dll" as a plug-in (loads the plug-in at runtime).
> In this scenario does  "a.dll", "b.dll" or "App.exe" become under LGPLv2.1 or later ? Does the source code corresponding to "a.dll", "b.dll" and "App.exe" become under LGPLv2.1 or later ?
> In case the answer is yes, which of these libraries/executable becomes under LGPLv2.1 or later ? Which part of the source code owned by me and used to compile above libraries become under LGPLv2.1 or later?

By "becomes under LGPL v2.1 or later" you probably mean "I am obliged
to publish full source code of". Otherwise your question makes little
sense. Actually, whatever you choose to do in relation to FFmpeg
libraries, inevitably falls "under LGPL v2.1 or above", only in some
cases there is nothing you should do or worry about.

If your "a.dll" is linked dynamically with FFmpeg libraries, you only
have to publish the exact source and instructions of how you built
these FFmpeg libraries. You cannot simply point to the FFmpeg website.

If "a.dll" is linked statically with FFmpeg libraries, you probably
should publish the source code and instructions of how you build this

IANAL, and there are some special situations, but this is the general
direction of LGPL.

Alex Cohn

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