21 ms·

Qt is lgpl. Unless I missed something, this should not be a problem whatsoever if you'd like to use the Qt framework and sell commercial software.

hjek 8y ago
Exactly. No problem whatsoever selling something made using Qt[0]. But there is a "problem" using Qt to release proprietary software, of course, because Qt is free, and perhaps parent isn't aware of the distinction between commercial and proprietary? [0]: https://www.gnu.org/philosophy/selling.html https://www.gnu.org/philosophy/selling.html
- SwellJoe 8y ago
  LGPL is not GPL. You're adding to the confusion by conflating them.
- munk-a 8y ago
  This is incorrect, using LGPL licensed software does not prevent you from keeping your software closed source, any components you rely on from Qt will need to be provided (or reference given which is a _really_ weak requirement) in open source but any functions referencing Qt functions do not themselves need to be provided in a decompiled form, this is pretty much why LGPL exists. So if you're company is trying to make money making proprietary improvements to Qt _which require you to edit Qt_ then you're a bit hooped, but I strongly suspect instead there was a misunderstanding which how contagious free software is. (That said, whenever possible please give back to the FSF community)
  - berti 8y ago
    Does #including (non-trivial) Qt headers make your software a derivative work? IIRC there is a decent amount of actual code in some of the headers. Seems like a very grey area.
    - deleted 8y ago
      [deleted]
    - munk-a 8y ago
      It does not, and with significantly complex header files (like the SIGNAL/SLOT macros Qt includes) this can seem like a grey area, but the LGPL specifically splits code into object & specification code, if your code directly references and links against publicly defined specification code you're in the clear... if you are doing this with knowledge of how specific object code works and manipulating that object code using your own code (i.e. intentionally overwriting a stake frame) I think that does become more of a grey area, but the intent of the license is very straightforward about allowing non-contagious use of interface specifications, that is what specifically makes it LGPL instead of GPL (the latter lacks that distinction and does not allow the use you're asking about among some other uses). This is of course complicated by SaaS and all that is covered in more detail in Affero license and in that field I'm out of my depth. Oh also, I am not a lawyer, if you're developing something commercially or otherwise reading this for advice please take a moment to consult a professional.
      - berti 8y ago
        Thanks, what you said makes sense, or licensing Qt under LGPL in addition to GPL would make no sense. > Oh also, I am not a lawyer, if you're developing something commercially or otherwise reading this for advice please take a moment to consult a professional. Absolutely!
StavrosK 8y ago
Can someone tell me in simple terms what the Qt licensing situation is? The webpage for Qt Design Studio says you can only use the designs you come up with in an app if you have a Qt commercial license.
- cpburns2009 8y ago
  It looks like Qt Design Studio is a commercial product that's free for evaluation only. > Qt Design Studio is available today as a free tool for everyone to try out and evaluate. You will need a commercial Qt developer license to distribute your UIs created with Qt Design Studio. > We are also working on an open source version with a limited feature set, to be published in December. The Qt library itself has both commercial and LGPL licenses. You can safely use LGPL libraries in commercial products with a couple obscure provisions: it's commonly held the library has to be dynamically linked, the user has the right to replace the Qt dynamic libraries, and maybe a few other inconsequential things.
mrpippy 8y ago
Specifically, LGPL3 since Qt 5.7. Big problem for people making embedded devices, but shouldn’t be for commercial software.
- exikyut 8y ago
  If the embedded device supports dynamically linked libraries, though, that could still work
  - joezydeco 8y ago
    As long as you can deliver the toolchain used to build the libraries, and allow the finished libraries to be installed on your target hardware over the current ones. I know one major vehicle manufacturer that won't go past 5.6 because of this reason. They put it right in the RFP.
    - reitanqild 8y ago
      Edit: I might be misunderstanding something here but: I'd think a major vehicle manufacturer should be able to pay for the commercial license?
      - joezydeco 8y ago
        Has nothing to do about the royalty fees. Those didn’t change from 5.6 to 5.7. It has everything to do with being required to allow end customers to install their own libraries on a piece of their machinery. LGPL 3 closed the LGPL 2.1 loophole concerning this. The legal and warranty issues around letting customers reflash their dashboards are what the company wants to avoid.
        reitanqild 8y ago
        But I thought that was part of what you got with the commercial license, a right to use it without adhering to the open source license?

hjek 8y ago

Exactly. No problem whatsoever selling something made using Qt[0]. But there is a "problem" using Qt to release proprietary software, of course, because Qt is free, and perhaps parent isn't aware of the distinction between commercial and proprietary? [0]: https://www.gnu.org/philosophy/selling.html https://www.gnu.org/philosophy/selling.html

SwellJoe 8y ago
LGPL is not GPL. You're adding to the confusion by conflating them.
munk-a 8y ago
This is incorrect, using LGPL licensed software does not prevent you from keeping your software closed source, any components you rely on from Qt will need to be provided (or reference given which is a _really_ weak requirement) in open source but any functions referencing Qt functions do not themselves need to be provided in a decompiled form, this is pretty much why LGPL exists. So if you're company is trying to make money making proprietary improvements to Qt _which require you to edit Qt_ then you're a bit hooped, but I strongly suspect instead there was a misunderstanding which how contagious free software is. (That said, whenever possible please give back to the FSF community)
- berti 8y ago
  Does #including (non-trivial) Qt headers make your software a derivative work? IIRC there is a decent amount of actual code in some of the headers. Seems like a very grey area.
  - deleted 8y ago
    [deleted]
  - munk-a 8y ago
    It does not, and with significantly complex header files (like the SIGNAL/SLOT macros Qt includes) this can seem like a grey area, but the LGPL specifically splits code into object & specification code, if your code directly references and links against publicly defined specification code you're in the clear... if you are doing this with knowledge of how specific object code works and manipulating that object code using your own code (i.e. intentionally overwriting a stake frame) I think that does become more of a grey area, but the intent of the license is very straightforward about allowing non-contagious use of interface specifications, that is what specifically makes it LGPL instead of GPL (the latter lacks that distinction and does not allow the use you're asking about among some other uses). This is of course complicated by SaaS and all that is covered in more detail in Affero license and in that field I'm out of my depth. Oh also, I am not a lawyer, if you're developing something commercially or otherwise reading this for advice please take a moment to consult a professional.
    - berti 8y ago
      Thanks, what you said makes sense, or licensing Qt under LGPL in addition to GPL would make no sense. > Oh also, I am not a lawyer, if you're developing something commercially or otherwise reading this for advice please take a moment to consult a professional. Absolutely!

StavrosK 8y ago

Can someone tell me in simple terms what the Qt licensing situation is? The webpage for Qt Design Studio says you can only use the designs you come up with in an app if you have a Qt commercial license.

cpburns2009 8y ago
It looks like Qt Design Studio is a commercial product that's free for evaluation only. > Qt Design Studio is available today as a free tool for everyone to try out and evaluate. You will need a commercial Qt developer license to distribute your UIs created with Qt Design Studio. > We are also working on an open source version with a limited feature set, to be published in December. The Qt library itself has both commercial and LGPL licenses. You can safely use LGPL libraries in commercial products with a couple obscure provisions: it's commonly held the library has to be dynamically linked, the user has the right to replace the Qt dynamic libraries, and maybe a few other inconsequential things.

mrpippy 8y ago

Specifically, LGPL3 since Qt 5.7. Big problem for people making embedded devices, but shouldn’t be for commercial software.

exikyut 8y ago
If the embedded device supports dynamically linked libraries, though, that could still work
- joezydeco 8y ago
  As long as you can deliver the toolchain used to build the libraries, and allow the finished libraries to be installed on your target hardware over the current ones. I know one major vehicle manufacturer that won't go past 5.6 because of this reason. They put it right in the RFP.
  - reitanqild 8y ago
    Edit: I might be misunderstanding something here but: I'd think a major vehicle manufacturer should be able to pay for the commercial license?
    - joezydeco 8y ago
      Has nothing to do about the royalty fees. Those didn’t change from 5.6 to 5.7. It has everything to do with being required to allow end customers to install their own libraries on a piece of their machinery. LGPL 3 closed the LGPL 2.1 loophole concerning this. The legal and warranty issues around letting customers reflash their dashboards are what the company wants to avoid.
      - reitanqild 8y ago
        But I thought that was part of what you got with the commercial license, a right to use it without adhering to the open source license?