pyqt4 & qt license

Discussion in 'Python' started by pitsakis@gmail.com, Mar 10, 2013.

  1. Guest

    hello,

    i want to develop a GUI application that will be sold.
    i want to use pyqt4.
    can i download and use the GPL version during the development and then buy the commercial verion beofore i distribute the application ?

    commercial version means LGPL? i think i am comfused so please someone clarify on versions and licences.

    somewhere i also noticed that there is a qt license ? will i need this also ?

    Thank you in advance
     
    , Mar 10, 2013
    #1
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  2. On Sat, Mar 9, 2013 at 9:08 PM, <> wrote:

    > hello,
    >
    > i want to develop a GUI application that will be sold.
    > i want to use pyqt4.
    > can i download and use the GPL version during the development and then buy
    > the commercial verion beofore i distribute the application ?
    >
    > commercial version means LGPL? i think i am comfused so please someone
    > clarify on versions and licences.
    >
    > somewhere i also noticed that there is a qt license ? will i need this
    > also ?
    >
    > Thank you in advance
    > --
    > http://mail.python.org/mailman/listinfo/python-list
    >


    I am not sure if this is the right place for clarifying Licences issues.
    But I am sure that you are "touching" a very sensitive issue about how to
    mix licenses for commercial products.
     
    Ioakeim Tellidis, Mar 10, 2013
    #2
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  3. CM Guest

    On Mar 9, 9:08 pm, wrote:
    > hello,
    >
    > i want to develop a GUI application that will be sold.
    > i want to use pyqt4.
    > can i download and use the GPL version during the development and then buy the commercial verion beofore i distribute the application ?


    Arguably, yes. From pyqt4's website:

    "Yes, you can re-license your application under a commercial license
    so long as you have purchased appropriate commercial PyQt licenses
    before you start to sell it."

    and also:

    "The availability of the LGPL version of Qt means that it is possible
    to evaluate using that and the GPL version of PyQt while still being
    able to re-license any code written during an evaluation in a future
    closed source application."

    > commercial version means LGPL? i think i am comfused so please someone clarify on versions and licences.


    There is currently no version of PyQT licensed with LGPL. They refer
    to their commercial license as
    their "commercial license".

    > somewhere i also noticed that there is a qt license ? will i need this also ?


    Yes. PyQT is a wrapper for Python around QT, so you would need both.
    QT has, according to the site,
    both a GPL and LGPL version of their license.

    You can read up on GPL and LGPL by Googling about it, but in a
    nutshell, for commercial applications,
    of the two, LGPL is what you want.

    Do you know about PySide? It's another wrapper for QT that is
    licensed as LGPL and is free software.
    I don't know it's current state of development, though. Last Twitter
    update was about a year ago.
     
    CM, Mar 10, 2013
    #3
  4. On 03/09/2013 07:08 PM, wrote:
    > hello,
    >
    > i want to develop a GUI application that will be sold. i want to use
    > pyqt4. can i download and use the GPL version during the development
    > and then buy the commercial verion beofore i distribute the
    > application ?
    >
    > commercial version means LGPL? i think i am comfused so please
    > someone clarify on versions and licences.


    Nope. Commerical means you buy a royalty-free license to use their
    product in a proprietary project. In other words you buy the right to
    use their code in a way that's compatible with your own code's
    distribution scheme.

    >
    > somewhere i also noticed that there is a qt license ? will i need
    > this also ?


    You must be aware of the licenses of each individual part of the stack
    and honor their terms! This is true of *any* library you use, and code
    from *any* source. Open source does not mean public domain and you
    don't automatically have a right to use it in your own project. If you
    are using open source components in a proprietary project, you might
    need to consult a lawyer if you are unsure of the use terms you are
    dealing with or your obligations under those terms under copyright law.

    You have to follow the appropriate license for Qt (LGPL, so no biggy for
    you if you don't modify Qt itself), PyQt (GPL only or proprietary
    royalty-free), Python itself (not a problem since you aren't modifying
    it and you can redistribute it), and any and all Python libraries you
    might use. From what I can tell things in the standard library are
    fine, but watch out for third-party libraries. The licenses are not
    always compatible with proprietary code.

    As for PyQt, unless you pay for the proprietary, royalty-free license
    for PyQT (before or after development), then you have to use the GPL for
    your project, since those are the terms the free version of PyQt is
    released under. This is a deliberate choice by the company that makes
    it to secure a revenue stream.

    There is an alternative to PyQt, PySide, which is under the LGPL and
    compatible with a closed-source project.
     
    Michael Torrie, Mar 10, 2013
    #4
  5. D. Xenakis Guest

    Please correct me if im wrong..

    PySide is LGPL and is free and by using that someone can develop commercial(and non commercial) software, while being able at the same to choose between both close and open Source.

    PyQT4 Commercial Licence costs more than 300 Euro and by using that someonecan develop commercial software while being again able to choose between both close and open Soruce.

    PyQT4 GPL Licence is free and by using that someone can develop only non-commercial software. What about the source here? Could that be both open and close?

    Can someone develop a closed source but NON-commercial software, by using PyQT4 GPL license?

    Τη ΚυÏιακή, 10 ΜαÏτίου 2013 5:31:21 Ï€.μ. UTC+2, ο χÏήστης CM έγÏαψε:
    > Yes. PyQT is a wrapper for Python around QT, so you would need both.
    >
    > QT has, according to the site,
    >
    > both a GPL and LGPL version of their license.


    If someone used PySide, he should again use in addition one of those 2 above QT licences?

    Last question: Could someone just buy the PyQT4 commercial licence and use the LGPL licence of QT in his CLOSED source commercial software? (Which i believe is free :S)

    Or does LGPL mean that the source should be open?

    Or i should better ask, Does any of those 2 Licenses cost any money? Or they are free?


    Forgive me for all these questions im very interested in this topic too.
    THX 4 your time!!
    Tellidis your Greek? :)
     
    D. Xenakis, Mar 10, 2013
    #5
  6. D. Xenakis wrote:

    > Can someone develop a closed source but NON-commercial software, by using
    > PyQT4 GPL license?


    no, by definition of GPL: if you are using a GPL library, you must
    distribute your software as GPL.

    (the GPL does not care about commercial / non commercial)

    http://www.gnu.org/licenses/gpl-faq.html#IfLibraryIsGPL

    --
    ZeD
     
    Vito De Tullio, Mar 10, 2013
    #6
  7. On 03/09/2013 09:45 PM, Vito De Tullio wrote:
    > D. Xenakis wrote:
    >
    >> Can someone develop a closed source but NON-commercial software, by using
    >> PyQT4 GPL license?

    >
    > no, by definition of GPL: if you are using a GPL library, you must
    > distribute your software as GPL.
    >
    > (the GPL does not care about commercial / non commercial)
    >
    > http://www.gnu.org/licenses/gpl-faq.html#IfLibraryIsGPL


    Just to be clear here, the GPL isn't a magical license. It doesn't
    arbitrarily infect your code and force you to use the GPL on your own
    code. And no matter what license you use, you can re-license your code
    later under any terms you wish, since you own the copyright on the code.

    Here's the vital part: The moment you distribute your code, if you use a
    GPL library, then unless you also release your code under the GPL also,
    you are now in a copyright violation situation. You have three options:

    1. License your code in a compatible way so that you're following the
    terms of the open source license the library you are using asks of you.
    IE release your source code under the terms of the GPL.

    2. Remove the GPL'd library and either implement the lost functionality
    yourself (also know as "write your own dang code"), or replace the GPL'd
    library with an equivalent library under a different, compatible
    license. In the case of PyQt, this could be PySide, or maybe you decide
    to use a completely different GUI toolkit.

    3. Negotiate a proprietary license with the copyright holder (IE buy the
    proprietary, royalty-free license from PyQt's authors.

    If you are in a position where you have violated copyright, failure to
    remedy it in a timely manner can cause you to be financially liable to
    the copyright holders of the code you are mis-using.

    Now, if you develop a program using PyQt and distribute it under the
    terms of the GPL, that does not mean you have to keep your code under
    the GPL. You can close your source at any time and use, say, PySide
    instead. But any code you already distributed under the GPL remains in
    the wild (supposing someone has a copy) under the GPL terms, even if
    newer versions of your software adopt a new license.
     
    Michael Torrie, Mar 10, 2013
    #7
  8. Guest

    Am Sonntag, 10. März 2013 05:09:41 UTC+1 schrieb D. Xenakis:
    > Please correct me if im wrong..
    > ...
    > PyQT4 GPL Licence is free and by using that someone can develop only
    > non-commercial software.

    Wrong. GPL does not prevent you from developing commercial softwarre. You just have to release your source under GPL.
    GPL is free as in freedom. It doesn't have to be free as in "free beer". There are customers paying for software relesed under GPL. They just needed it and didn't care if others used it too.

    > What about the source here? Could that be both open and close?

    As already said, if you use parts of GPL code in your (non private) project, the whole project has to be GPL.

    > Can someone develop a closed source but NON-commercial software,
    > by using PyQT4 GPL license?

    GPL does not cover commercial vs. non-commertial. Just freedom vs. proprietary.

    > ...


    hth,
    Martin
     
    , Mar 10, 2013
    #8
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