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Can Qt opensource be used for some application i can sell ?

  • Hi,

    if anybody have some Idea that, under LGPL or GPL i can sell my application (with redistributable Qt dlls/libs), which i've developed from Qt Open source (free license). or i do require Qt commercial license? i m not not changing the Qt libs/source code.

  • It is ok to sell you application that has been written using Qt when:

    1. your application is dynamically linked to Qt libs
    2. the original source of Qt has not been modified

  • LGPL and GPL are rather different when it comes to linking libraries... in fact that is the mayor difference between those two licenses!

    You are running the risk of getting sued if you do something wrong, so in your place I would not trust random people on the internet:-) I would recommend reading the licenses yourself (and if you are doing this commercially maybe even get a lawyer to look at them). Laws do differ in different countries, so what we tell you here may or may not be applicable in your place.

    "Translations of the LGPL and GPL licenses":http://www.gnu.org/licenses/translations.html are available on the FSF gnu site.

  • Tobias Hunger, is not it enough to use qt libraries under LGPL?

    [quote author="lyuts" date="1285743589"]

    1. your application is dynamically linked to Qt libs
    2. the original source of Qt has not been modified[/quote]

  • Alexander Kuchumov: I think it is, but:

    1. I am not a lawyer
    2. I do not know the country/legislation pushpendrak is working under.
    3. I do not know what pushpendrak actually wants to do and which license he wants to use for his code
    4. I do not know if there are additional requirements with regard to licensing (e.g. regulations imposed by his customers, etc).
    5. Whether other libraries are getting used and which license those are using.
    6. It is generally a bad idea to trust random people on the net on legal advise.

    So I will not charge forward and claim everything will be fine, even though I think it should. If you want to get into the selling-software business you need to do your own reading:-) Getting legal advise also does not hurt: Not only to make sure that you are not breaking licenses yourself but also to come up with a working license for the part of the code you own.

  • I see. It's tough question:)

  • The lesson learned is "Make opensource software, not proprietary" :)

  • lyuts: You can have just as much fun in open source: Just look around how many open source licenses there are and how many opinions on which of those are compatible with each other. Check the flamewars going on with one party accusing the other of not following the license of some piece of code. Some of those even are about perceived breaks of "the spirit of the license", not any concrete clause of it!

    Basically licensing is a legally tricky and highly emotional topic. So you do need to form your own opinion about it sooner or later.

    I think we got widely off-topic:-)

    Just to make this clear: Qt's open source licensing is pretty straight forward and compatible with most use cases, using either LGPL or GPL. Both are pretty well understood and widely used. There still are reasons to use a commercial Qt license (if you want to ship modified Qt versions without providing the changes done, etc.). I am sure the Sales team will be competent in answering any questions related to these issues.

  • Thank u Tobias

    wot u said is correct, i should look for some legal person. okey.
    that means if i m not changing the Qt code, i can do anything with my application whether sell or distribute freely or make it opensource.

  • Thanks MariusG, it is very helpful to me......

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