Using/Buying Qt SDK (including Qt Creator etc.)

| | August 5, 2015

I am currently learning C++ (and I know I must learn everything before creating GUI apps, on perhaps console first, but)

While doing some searching for an SDK -which would help with creating the GUI of my app – letting me write JUST the important codes myself-, I found, downloaded, and installed a C++ IDE; Qt SDK (Qt Creator Trial for 30-days; version 2.5.2, based on Qt 4.8.2).

My questions are:

  • If I like the app, and the trial expires and I want to buy the app, how much would a license cost me? If any of you guys have used, or use this app, how much did you spend? (I’ve checked their website, which to be honest, is very intimidating, and includes no info about pricing etc.)
  • Which license would be adequate for me creating apps and selling them online, from a website. (I obviously want to avoid buying the wrong license and getting into trouble!)

If you can help me, thank you! If this is a non-question or is unsuitable for this website, please just give me references etc. :)


NOTE!

My apps would be closed-source (commercial, not free, with the exclusion of some). I would guess that this would affect which license terms/types apply to me.

Also, when and if I do buy the software, do I have to mention I used it or give any references etc.??


CLARIFICATION

To clarify, me needs are as follows:

  • My software may or may not be free (there may both free and paid versions of each)
  • My software’s source should not be available, and I specifically want my application to be closed-source i.e. no one should have access to the source code that was used to build it.
  • I will be selling/distributing my software from a website (a company website).

One Response to “Using/Buying Qt SDK (including Qt Creator etc.)”

  1. Instead of downloading the trial for the commercial license version, download the free version here. Note the information at the top right of that page:

    Qt is available under GPL v3, LGPL v2 and a commercial license. Learn more about licenses here.

    As per the comments on your question, there are licensing options available which are suitable for closed-source commercial applications. The main limitation IIRC is that you must not use static linking for the non-commercial licenses. Have a look here and here to learn more about static vs dynamic linking. The Qt binary packages on the above link are already compiled for dynamic linking, so you don’t have to worry about it if you use it off-the-shelf (as opposed to compiling it yourself). When you deploy your application, just make sure to include the relevant dynamic library files (.DLL on Windows).

    Other than the links on the Qt website, you can research more about the license types here:

    GPL

    Wikipedia.

    GNU.

    LGPL

    Wikipedia.

    GNU.

    From what you’ve described in your edits and your comments, it would seem that the LGPL (free) license is suitable for you. From Wikipedia:

    The LGPL allows developers and companies to use and integrate LGPL software into their own (even proprietary) software without being required (by the terms of a strong copyleft) to release the source code of their own software-parts. Merely the LGPL software-parts need to be modifiable by end-users (via source code availability): therefore, in the case of proprietary software, the LGPL-parts are usually used in the form of a shared library (e.g. DLL), so that there is a clear separation between the proprietary parts and open source LGPL parts.

    Note that this enables your users to update/modify the Qt dependencies, but without giving them the ability to view or modify your source code which is built on top of Qt. If this is not desirable to you, you need to use static linking and purchase the commercial license.

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