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Thread: Things to inlcude in an LGPL distribution

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    Default Things to inlcude in an LGPL distribution

    I know the board can't give legal advice, so I hope my question doesn't really need a 'legal advice' type response.

    I have written a simple program that may be of use to other people in my field. I am not interested in trying to get a fee for its distibution. From reading the LGPL license, and from reading other posts on this board, does the following sound about right for what I need to gve a third party if they want to use my program:

    1) A copy of the executable
    2) The dll files (QTcore4.dll, etc)
    3) A copy of the LGPL 2.1 license
    4) The .o files
    5) A link to where to get a copy of QT, should they want to rebuild the program with updated QT libraries

    I'd rather not distribute my source code, not that it is 'top secret' or particularly original, but I don't want other people to simple copy it and take credit for it. The majority of the code was written in 'normal' C++ originally (using CodeBlocks), and I've just used QT to build a gui for it (effectively), so I don't believe I have modified the QT libraries.

    Thanks in advance (if you can help).

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    Default Re: Things to inlcude in an LGPL distribution

    You don't need 4 if you dynamically link (which you do, bacause of 2)
    Further if you have somewhere a copyright notice that the program belong to you, you have to put a statement there that you use Qt and name the copyright for it.

  3. The following user says thank you to Lykurg for this useful post:

    The physicist (7th January 2011)

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    Default Re: Things to inlcude in an LGPL distribution

    Quote Originally Posted by Lykurg View Post
    You don't need 4 if you dynamically link (which you do, bacause of 2)
    Further if you have somewhere a copyright notice that the program belong to you, you have to put a statement there that you use Qt and name the copyright for it.
    That's great, thanks. So if I was to put a statement something like

    "Copyright Me 2011

    Developed using QT v4.x Copyright Nokia 2011"

    or similar, would that cover it?

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    Default Re: Things to inlcude in an LGPL distribution

    I think you don't need "3" as well unless you publish your application under LGPL. You only need to state in your docs (or in your program) you're using Qt under LGPL. Qt's "AboutQt" dialog can probably be used for that.
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    Default Re: Things to inlcude in an LGPL distribution

    Ok, puzzeled again. The v3.0 clearly says you need to provide a copy of the license. In v2.1 I don't find that term, but in the "how to apply" they write
    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
    Since the text is so small I would include it somewhere, just to be sure. But as always: Ask you lawyer if you have to

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    Default Re: Things to inlcude in an LGPL distribution

    Quote Originally Posted by Lykurg View Post
    Ok, puzzeled again. The v3.0 clearly says you need to provide a copy of the license. In v2.1 I don't find that term, but in the "how to apply" they write
    Since the text is so small I would include it somewhere, just to be sure. But as always: Ask you lawyer if you have to
    Oh, there's a v3.0 now is there!

    To follow on from wysota, is the inclusion of the LGPL license soley for the distribution of the QT dlls with my program? And then, if I don't want to distribute my program under LGPL, I can just apply a copyright statement?and distribute it as is?

    I shall try and seek legal advice anyway, and if I get a useful response, I shall let you all know...

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    Default Re: Things to inlcude in an LGPL distribution

    I'd probably create a text file called 'licenses.txt' or similar and inside state something like:

    'QtCore4.DLL, QtGUI4.DLL, ... <the entire list of DLLs you use from Qt>' are Copyright (C) 2011 Nokia. Used under license. See LGPL_License.txt for further information.'
    'MyApp.EXE is Copyright (C) 2011 Me, and is licensed under the Beerware license. See Beerware.txt for further information'

    Something like that should stop all ambiguity, but of course I'm no lawyer, so don't take this as legal advice.

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    The physicist (7th January 2011)

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    Default Re: Things to inlcude in an LGPL distribution

    Quote Originally Posted by Lykurg View Post
    Ok, puzzeled again. The v3.0 clearly says you need to provide a copy of the license. In v2.1 I don't find that term, but in the "how to apply" they write
    Since the text is so small I would include it somewhere, just to be sure. But as always: Ask you lawyer if you have to
    I always hate when someone uses the word "should" in a legal or otherwise formal document.

    Quote Originally Posted by The physicist View Post
    To follow on from wysota, is the inclusion of the LGPL license soley for the distribution of the QT dlls with my program?
    Yes.
    And then, if I don't want to distribute my program under LGPL, I can just apply a copyright statement?and distribute it as is?
    We're not sure. You can dump a copy of LGPL (in English) somewhere in the archive just to be sure. It won't hurt.

    I shall try and seek legal advice anyway, and if I get a useful response, I shall let you all know...
    Just be aware that the number of interpretations of (L)GPL is more or less equal to the number of lawyers interpreting it.
    Your biological and technological distinctiveness will be added to our own. Resistance is futile.

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  11. The following user says thank you to wysota for this useful post:

    The physicist (7th January 2011)

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    Default Re: Things to inlcude in an LGPL distribution

    Thank you all for your help.

    In practice, how does the dynamic linking actually work - If the dlls are updated, can the old ones simply be replaced with new ones, and the same executable will work with them?

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    Default Re: Things to inlcude in an LGPL distribution

    If they are released as binary compatible (eg. minor versions), yes. There is no need to recompile or relink the application.

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    Default Re: Things to inlcude in an LGPL distribution

    At least in theory
    Your biological and technological distinctiveness will be added to our own. Resistance is futile.

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    Default Re: Things to inlcude in an LGPL distribution

    Thanks again squidge and wysota.

    Is there anything in the QT LGPL licensing that says it can't be used by companies/organisations? Or is it literally just for the distribution/modification of the libraries? I'm guessing you both have corporate licenses and don't have these problems

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    Default Re: Things to inlcude in an LGPL distribution

    It is the LGPL, not the "Qt LGPL". So Qt can be used as any other library that is licensed under the GNU LGPL, to name it correctly. And the LGPL is just about how to use/modify it and does not say anything about who use it. So there is no limitation in that point.

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    The physicist (9th January 2011)

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    Default Re: Things to inlcude in an LGPL distribution

    So, (in theory) my program should run with updated dlls.

    In practice, how would someone relink my application without my source code if I supplied them the object files? This http://www.cis.temple.edu/~ingargio/cis71/ta/objectlib.html makes sense from a command line point of view, but I'm not sure how you would do it with QT

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    Default Re: Things to inlcude in an LGPL distribution

    Quote Originally Posted by The physicist View Post
    how would someone relink my application without my source code if I supplied them the object files?
    By simply replacing the Qt dll's with his own/modified ones.

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    Default Re: Things to inlcude in an LGPL distribution

    Quote Originally Posted by Lykurg View Post
    By simply replacing the Qt dll's with his own/modified ones.
    Oh, that simple

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    Default Re: Things to inlcude in an LGPL distribution

    The object files would only be needed if you statically linked, then its upto them how to relink them to create a new executable. No one will bother, but at least you complied with the license by giving them the option.

    Of course, object files are not necessary (even legally) for dynamically linked builds as you can just change the DLL.

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    Default Re: Things to inlcude in an LGPL distribution

    Thanks once again guys.

    Not that I plan on moving to MS Visual Studio, but how does anyone know how the licensing works with applications developed with that? Is it the same as with the commercial license of QT?

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    Default Re: Things to inlcude in an LGPL distribution

    A licence is a licence. It doesn't matter what tools you use. LGPL doesn't care. It only says about redistributing the licenced component.
    Your biological and technological distinctiveness will be added to our own. Resistance is futile.

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    Default Re: Things to inlcude in an LGPL distribution

    I was just thinking about 'what' libraries are actually 'QT' libraries. The libraries in my project are:

    libgcc_s_dw2-1.dll
    mingwm10.dll
    QtCore4.dll
    QtGui4.dll

    I assume that the QT libraries are definitely part of the LGPL licence, but are the mingw and libgcc ones? They all came out of the QT installation folder...

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