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Thread: qt 4.5 and above license issue..

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    Default qt 4.5 and above license issue..

    hi... i want to know suppose i started using qt 4.5 and higher[in LGPL] and developed/developing a software but now i want to buy qt due to some reason can i migrate my software that i am developing or already developed to the qt with the commercial license. and if i buy qt did i have to give them a upgrade fee for every new version of Qt.

    and also is it true that when i will be using lgpl qt then i have to make all the library link dynamic(qt libraries) and make the source code of those library open source and i also have to give away the object file of the program without the source code that i have written(i am not changing the qt library)

    with regards
    orky...

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    Default Re: qt 4.5 and above license issue..

    ...in regards to the first part of your question...

    According to the Qt License FAQ - you cannot switch from LGPL to commercial:
    http://www.qtsoftware.com/about/lice...-i-switch-from

    Can I switch from using Qt under the LGPL to commercial afterwards?

    Users of the LGPL versions of Qt need to comply with the LGPL licensing terms and conditions. Qt’s commercial license agreement contains a restriction that prohibits customers from initially beginning development with the LGPL licensed version of Qt and then transitioning to a commercial version of Qt.
    The Qt commercial license is based on a yearly support contract after the initial purchase. That means you pay up front the cost of the license and you renew each year based on the support cost. I can't remember the pricing for it right now - it's on their website or you need to inquire from one of the sales people.

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

    orky7 (1st June 2009)

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    Default Re: qt 4.5 and above license issue..

    Qt Software can say what they want but according to me you are the owner of the code so you can re-licence whenever you want. At worst you will change the application name and/or release a new version of the software.

    and also is it true that when i will be using lgpl qt then i have to make all the library link dynamic(qt libraries) and make the source code of those library open source
    Yes, you can't link LGPL components statically in closed-source applications. You don't have to provide the source code for LGPL components as long as you don't modify their source.

    and i also have to give away the object file of the program without the source code that i have written(i am not changing the qt library)
    No, this you don't have to do. Your application is still closed-source and licenced the way you choose it to so you are not obliged to share its code (neither source nor binary) with anyone.
    Your biological and technological distinctiveness will be added to our own. Resistance is futile.

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    Default Re: qt 4.5 and above license issue..

    thanks for the answers.....but thats bad that i can't convert my license as Qt is very expensive and i dont know whether my software will make grounds or not to make money..and with lgpl i can sell it my product but there are lots of nitty gitty..
    and if i dont want the support will the cost of renewal/purchase come down, actually i dont need any kind of support at all[due to money factor].

    as @"wysota" stated can i really do that...i mean can i first make the software if its catching ground then buy a licensed Qt and relaunch the software with different name or version.....

    P.S: Qt is very very expensive almost $3000 one user one platform as compared to visual studio which cost $800 around. no no i am not gona use VS coz of price i really hate it.
    Last edited by orky7; 1st June 2009 at 20:52.

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    Default Re: qt 4.5 and above license issue..

    My understanding is that you can use LGPL if you dynamically link the Qt to your application. Basically it means you can't modify the Qt source codes... You can still have a closed software product...

    If you do modify the Qt source codes, you must release the modified source of the Qt part...

    Please correct me if I am wrong...

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    Default Re: qt 4.5 and above license issue..

    Quote Originally Posted by orky7 View Post
    as @"wysota" stated can i really do that...i mean can i first make the software if its catching ground then buy a licensed Qt and relaunch the software with different name or version.....
    There used to be a special catch when talking about licencing with the Trolls. Sometimes they allowed you to switch to commercial licence if you paid the fee for the whole time-life of your application as (L)GPL. So if you developed an application under GPL for two years and wanted to switch to commercial, you'd have to pay for those two years and for the next year (as usual).

    P.S: Qt is very very expensive almost $3000 one user one platform as compared to visual studio which cost $800 around.
    Could you remind me how expensive is Visual Studio for Linux or for Mac?

    By the way, there is also a question what you get in return for that $800 and that $3000...
    Your biological and technological distinctiveness will be added to our own. Resistance is futile.

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    Default Re: qt 4.5 and above license issue..

    yup @ "wysota" u r right with Qt u get lots of freedom as well as platform independence that's why u have to pay a price i admit.
    u have to lie to Qt if u have already developed a project saying that it just started few months back they are not going to figure it out, but one should not do that its the issue of ur karma.
    @"lni" u r partially right u have to give the source code of the lgpl library to the user whether u modify it or not, and also u have to give the object file so that if the user want to use a new version of the lgpl library they can again recompile the project and make a better one u dont have to give the source code of the code that u have written. That's the reason u cannot give warranty of ur product to ur client/s.

    Can i buy Qt without the support as the cost of support is too much i just want the product.ya i had already written a mail to Qt few days back about this issue but till now no reply.so can i do it.

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    Default Re: qt 4.5 and above license issue..

    Quote Originally Posted by orky7 View Post
    @"lni" u r partially right u have to give the source code of the lgpl library to the user whether u modify it or not, and also u have to give the object file so that if the user want to use a new version of the lgpl library they can again recompile the project and make a better one u dont have to give the source code of the code that u have written. That's the reason u cannot give warranty of ur product to ur client/s.
    Qt is open source, when Qt release new version, it is likely that you will update your own codes (or better yet, make your own codes backward compatible), so your codes will work with each new Qt release forward, all you need is to send your new DLL to your clients (or do nothing if your code is already backward compatible). You have to do this even if you acquire a Qt commercial license anyway...Since cost is your concern, I don't really see why you can't use LGPL...

    you don't give your clients Qt source codes. If they need it, they can download from qtsoftware.com themself and build their own Qt libraries......

    If you don't plan to follow Qt development and provide compatible DLL with any future Qt release, then your software won't last. It is like a time deal...

    When you sell your software, you also collect annual license renewal fee, so that you can provide then updated DLL...you stay live with Qt in this case... If they don't pay renewal fee, your client don't get updated DLL, that is their problem...

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    Default Re: qt 4.5 and above license issue..

    yup @"lni" u r right.
    There are lots of nitty gitty with lgpl and the size of my software will be large since i have to ship all the used libraries as stated in lgpl u cant ship a part of the library, for this headache reason i really love postgreSQL and SQLite no tension just use them. some day when i have a good job i will definitely make a donation to them i really love to buy Qt but oh my god the cost, so for the time being lgpled Qt will be my friend....

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