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I want to use portions of code from the FFMPEG library to provide screen capture function for a commercial application I'm writing. I do understand I need to make a shared library out of the function or it'll make the entirety of our application LGPL, fair enough. The library part will be LGPL with the usual LGPL 2.1 notices and source code availability.

After I'm done chopping the function(s) to suit my use case, it will not really function in a meaningful way in the context of the FFmpeg anymore. I want a series of discrete bitmaps for processing display contents, not a constant video stream that will be encoded or displayed. So it probably does not make sense to provide it as a contribution to the FFmpeg project.

What should I exactly write in the copyright notice? The original says 

/*
 * XCB input grabber
 * Copyright (C) 2014 Luca Barbato <[email protected]>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.

etc.

In my derived source code I should keep Luca's copyright line as-is and add mine under it? I change the "FFmpeg" to say "MyExcellentScreenCaptureLibrary" and add a note somewhere saying this is based on the FFmpeg XCB input grabber code?

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  • This seems to boil down to the LGPL 2.1's requirement to "keep intact all the notices that refer to this License" -- does the change of only a project name (FFmpeg => myGreatLibrary) violate this requirement? I don't know. Certainly, though, you must preserve the existing copyright notice, and you should add your own alongside, yes.
    – apsillers ♦
    Feb 28, 2018 at 18:43
  • I guess I could just put "original copyright notice follows" line there.
    – Barleyman
    Mar 6, 2018 at 10:23

1 Answer 1

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In my derived source code I should keep Luca's copyright line as-is and add mine under it?

Normally, that's what you'd do. In this case you can do exactly that and be done with it, but the "This file is part of FFmpeg." line then becomes a bit odd in your context. Can you change this line? Not if it is considered a part of the original copyright notice. Is it? I don't know.

The way I see it you have three options.

1) Add your copyright line under Luca's and accept the strangeness.

2) Figure out if you are allowed to change the problematic line nor not, if you are, change it and add your copyright line under Luca's.

3) Keep the original header as it is, add a line above saying something like "Portions of this file originate from FFmpeg, original copyright header:" and then add your own copyright header separately.

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    Legally, the line "This file is part of FFmpeg" is neither part of the copyright line (which must start with the wordt Copyright), nor is it part of the license. Thus you are free to change it.
    – Bart van Ingen Schenau
    May 5, 2018 at 17:29
  • The LGPL 2.1 doesn't even mention the term "copyright line". It does, however, mention "copyright notice" several times. I would be very careful making assumptions about any universal rules regarding what such a notice is or isn't and I would ask anybody who claims otherwise to back their claim up somehow. Would you mind doing that?
    – Mans Gunnarsson
    May 6, 2018 at 17:52
  • Is the US law (where the use of copyright notices originated) good enough: 17 U.S.C. § 401(b). All other (also non-US) references refer to the same format. And you are right that I should have been more precise in my previous comment regarding how to call the copyright notice.
    – Bart van Ingen Schenau
    May 6, 2018 at 18:39

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