How does Qt work with a indie developer?



  • I'm a little fuzzy about Qt's relationship with me as a Indie developer. Say I want to make a game engine that will use Qt as its foundation. I make a game with my engine, using Qt as the foundation. Can I submit the game without paying for Qt Enterprise?


  • Moderators

    In essence, you have 3 choices with Qt:

    • choose the commercial license - this means you need to pay Digia and thus help Qt grow, in return you get service from Digia (tailored help, faster bug fixes, etc.) and are free to choose any license for your own code (your game)
    • you can take Qt as LGPL - under that license, you do not need to pay anybody and you are free to choose any license for your own code (including closed-source licenses). The rules are: you have to allow swapping of Qt DLLs (that more or less means no static linking of Qt), you have to include Qt license file with your project and clearly state inside your game/ readme, that this project is using Qt. If you change anything in Qt (say, you patch QString), you need to publish those changes (exception: small changes)
    • you can take Qt as GPLv3 - with that license you (again) don't need to pay anybody, but you are obliged to use GPLv3 for your application, too (that is, it has to become Free Software, too). So, you need to provide the source code of your application (and Qt) to your clients on request (you do not need to publish them globally). The benefit is that you can use static linking in this scenario

    In all 3 scenarios you can sell your game/ application: the GPL family of licenses are not concerned with money.

    Hope this helps. Feel free to ask more if anything is not clear.



  • I just got back a email from Qt that stated that since apple doesn't allow dynamic libraries to be in a published app:

    bq. For iOS you will need a Qt commercial license, as the Apple App store has a policy of not allowing libraries, which for Qt developers means that the LGPL version is not allowed.eq.

    So, the million dollar question is, how much is a Qt commercial license?

    Is this the $149 per month developer cost?



  • I have to say, I don't mind paying a 1 time fee (if its reasonable) to use Qt's commercial license.

    But any app you make for mobile is high risk it will generate $0 dollars. I certainly have reservations of publishing a app that makes $0 dollars AND have to pay Qt a monthly fee.

    Thats called stupid-talk.


  • Moderators

    I have heard compiling statically is ok for LGPL, as long as you distribute the object files of your code to the customers. So maybe that is also an option. Mightily inconvenient, but it might work for you (don't take my word for whether it's legal, thought, treat it more like rumour).

    For licensing costs, you need to contact Digia.



  • I have a email sent to Qt to inquire about current costs.

    The sad fact is, there are great engines out there that are pretty darn cheap to use such as unity and UDK. And Qt, if it wants to compete, needs to examine their pricing models and decide if they can compete in that market.

    I am a bit of a masochist and take a bit of pride in my skill set. I want to know the nuts and bolts of the engine. And I can write a engine exactly suited to my needs without paying any royalties to an engine maker.

    What attracted me to Qt is the multi-platform handling. Period. And even if I don't ship my game with it, I will use it in my tool pipeline.

    I'm waiting to see what Qt customer service says about pricing...



  • So, Digia got back with me. to release a game (or any product) on iphone requires that you use Qt's static libraries. (This is not Qt's requirement. Its Apples. this restriction is not true for Android.) This then makes it mandatory to own a commericial license of Qt to publish on iPhone.

    The cost is $149 per month per this "link..":http://qt.digia.com/buy/

    There are still unanswered questions. Like, can I buy the commercial license once my game is done? I've got months of work ahead of me. Can I buy the license at the end just before I publish?

    I may end up just using Qt in my tools pipeline, and keep my engine Qt free.


  • Moderators

    [quote author="kloveridge" date="1400776930"]There are still unanswered questions. Like, can I buy the commercial license once my game is done? I've got months of work ahead of me. Can I buy the license at the end just before I publish?[/quote]

    I don't know the exact details for the monthly contract. But I suspect what you write is legal and valid. While you develop, the project is not published, so neither Apple nor Digia should have anything against it. But please don't take my word for it, better get the answer from Digia.


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