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Old comercial app and qt5 licensing



I need help regarding qt licensing.
We distribute a system (hardware and software) PC, tablets etc. On PC OS is Linux and contain a 6 years old program made in Lazarus.
If somebody encounter a similar situation, please help me to know what to expect. This is a preparation phase, probably nothing will be done in the next 3 months.
The original development team is no longer available, the (external) firm responsabile was closed two years ago, but we will have the source code in 1-2 months.

gtk+ 2 is end of life and not maintained anymore. gtk+3 is not ready in Lazarus. It might be necessary to switch to qt5 in the next 12-24 months when gtk2 will be removed from distros.
If we try to switch lcl to qt5 what licensing issues to expect ?
Based on what I read it is legal to distribute software commercially dynamically linked to unmodified LGPL QT5. Is that correct ?

We do not have any modified qt5 library, prefer to not distribute source code and can not afford ~10000€ (VAT included) Qt5 commercial license for 3 years.
Can we use qt5 licensed under LGPL dynamically linked ?
Do Lazarus static link anything regarding qt5, anything than qt5pas library ?

Right now, I can test only gtk+ version.

--- Code: Bash  [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---ldd test_prg (0x00007ffe841a6000) => /usr/lib64/ (0x00007fb7b28e5000) => /usr/lib64/ (0x00007fb7b248f000) => /usr/lib64/ (0x00007fb7b232e000) => /usr/lib64/ (0x00007fb7b22fd000) => /usr/lib64/ (0x00007fb7b2295000) => /usr/lib64/ (0x00007fb7b212c000) => /usr/lib64/ (0x00007fb7b2125000) => /usr/lib64/ (0x00007fb7b211f000) => /usr/lib64/ (0x00007fb7b20bd000) => /usr/lib64/ (0x00007fb7b1f40000) => /usr/lib64/ (0x00007fb7b1f0b000) => /usr/lib64/ (0x00007fb7b1f02000) => /lib64/ (0x00007fb7b1d0d000) => /usr/lib64/ (0x00007fb7b1cfc000) => /usr/lib64/ (0x00007fb7b1c12000) => /usr/lib64/ (0x00007fb7b19e0000) => /usr/lib64/ (0x00007fb7b1988000) => /usr/lib64/ (0x00007fb7b1891000) => /usr/lib64/ (0x00007fb7b1882000) => /usr/lib64/ (0x00007fb7b186c000) => /usr/lib64/ (0x00007fb7b185c000) => /usr/lib64/ (0x00007fb7b184d000) => /usr/lib64/ (0x00007fb7b1848000) => /usr/lib64/ (0x00007fb7b1843000) => /usr/lib64/ (0x00007fb7b1838000) => /usr/lib64/ (0x00007fb7b181f000) => /lib64/ (0x00007fb7b174a000) => /usr/lib64/ (0x00007fb7b172f000) => /usr/lib64/ (0x00007fb7b1701000) => /usr/lib64/ (0x00007fb7b16ae000) => /usr/lib64/ (0x00007fb7b16a2000) => /lib64/ (0x00007fb7b1625000) => /usr/lib64/ (0x00007fb7b1606000) => /usr/lib64/ (0x00007fb7b14c7000) => /usr/lib64/ (0x00007fb7b14b4000) => /usr/lib64/ (0x00007fb7b14ad000) => /usr/lib64/ (0x00007fb7b149d000) => /lib64/ (0x00007fb7b147e000) => /usr/lib64/ (0x00007fb7b13f7000)        /lib64/ (0x00007fb7b29b8000) => /usr/lib64/ (0x00007fb7b13ce000) => /lib64/ (0x00007fb7b1382000) => /usr/lib64/ (0x00007fb7b134e000) => /lib64/ (0x00007fb7b1344000) => /lib64/ (0x00007fb7b132a000) => /usr/lib64/ (0x00007fb7b1325000) => /usr/lib64/ (0x00007fb7b131a000) => /lib64/ (0x00007fb7b12ee000) => /usr/lib64/ (0x00007fb7b1236000) => /usr/lib64/ (0x00007fb7b1202000) => /lib64/ (0x00007fb7b11c4000) => /usr/lib64/ (0x00007fb7b11a5000) => /usr/lib64/ (0x00007fb7b1194000) nm test_prg nm: test_prg: no symbols
When will have the source code, what else to test to be sure that we are compliant ?

Thank you!

Qt5 is LGPL, so yes you can use it for your commercial apps.

Thank you for confirmation.

So, I should not worry about static linking in Lazarus ? Everything is dynamically linked ?

QT licensing has already been discussed:,55440.msg415530.html#msg415530,49100.0.html

Thank you very much!
Everything is clear now.


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