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I strongly agree with this, with one caveat: there are a few modules that are GPL and not LGPL. Definitely check the module licenses to make sure you're not going to need anything that is GPL. Most likely you won't.

On an unrelated note, as someone who mainly builds desktop tools and has used Qt for many many years, but would like to get away from C++ for UI logic, I can't see any reasonable alternative, but would love for some suggestions.

Qt just makes so many things easy, and basically every use-case is well-explored. Most other options seem to just focus on making easy things easy. As soon as you want to render something in 3D, make a node editor, call into or share data with C++ libraries, implement a reasonable undo/redo system, re-skin the UI to not look like a children's app, etc, other options fall flat.

True, some modules are under the GPL only. Here[0] is a very nice website showing an overview.

As for alternatives there really is not much to choose from. For small projects which are not reliant on the performance/native designs of Qt, Dear ImGui looks nice[1]. But it is very much tailored for a different Use Case.

Edit: I said that [0] is a nice website. But you only get a complete view of the situation if you cycle through all of the open source licenses. Too bad there is no "Open Source" option. Would hurt their sales I guess...

[0] https://www.qt.io/product/features

[1] https://github.com/ocornut/imgui

> used Qt for many many years, but would like to get away from C++ for UI logic

i've been thinking about this lately.

objc/nextstep got swift.

c/gobject got vala.

c++/serenity is getting jakt.

these are all higher-level compiled languages whose design is directly informed by the corresponding framework apis.

especially in the olden days, when qt wasn't as much c++ as moc/c++, it would have definitely seemed like there was another language in there. why hasn't it been extracted?

> programs you have to make sure you don't integrate or communicate with a program which uses the LGPL variant[0]. Yes that's right, if you pay them money you better make sure that you never run your program on KDE because it would inadvertently communicate with software that you are not allowed to communicate with

Wow, you seem right. That's incredibly dumb. It almost seems auto-destructive.

The commercial variant of Qt is designed to appeal to big players like car manufacturers. Not your small startup which is building a desktop app.

If car manufacturers would decide to support upgrading the Qt version by uploading shared objects directly to the car there would be no need for them to buy Qt Licenses. Because technically they could support all points of the LGPL. But that will never happen for two reasons:

1) It is very hard to get out of the contract if you already bought a license. You would have to prove that you aren't using any commercial tools anymore (of course they are the same tools as GPL but installed a different way).

2) They are car manufacturers and known to lock down their systems as much as possible.

The Qt Company probably didn't think about the average C++ Developer or Desktop programs at all while writing these Terms and Conditions...

Author here. Can confirm, I asked my boss (small German company with 7 employees) about getting Qt commercial license, because the Qt3d engine is still unusable slow and QtQuick3d looked like a nice alternative. Our product isn't even out yet, and we would have to pay 100k+ without having earned a single penny so far. We now switched to an embedded WebView Godot version for our 3d needs inside our qml desktop app.

Probably the better solution. It is an understatement how hard it is to get out of the commercial licence. If you would find out later that it isn't for you (or the Qt Company raises their prices again, like what happened from v5 to v6).

You even require written permission from Qt to upgrade from LGPL to the Commercial License[0]. Because if you started programming without paying them their fees you probably owe them even more money according to them...

[0] https://www.qt.io/faq/tag/qt-commercial-licensing (If I have started development of a project using the open source version (LGPL), can I later purchase a commercial version of Qt and move my code under that license?)

They are car manufacturers and known to lock down their systems as much as possible.

Have you ever tried to explain the Qt licensing system to the legal department of an automotive, medical, or aerospace manufacturer? I have.

If you can get them to understand it, their faces turn white at the idea of the end customer sideloading new libraries into the device. The conversation pretty much stops there.

Do small startups make desktop apps? I thought they only did phone apps or websites into electron.

They sure do. Many of my customers are small companies or startups shipping desktop apps, they come to us to get a tool that takes the pain out of desktop distribution [1]. Often they're doing things with hardware. Electron apps do count but actually a lot of our users aren't using it.

https://hydraulic.software/

> [0] https://embeddeduse.com/2023/01/06/using-qt-5-15-and-qt-6-un...

That is an excellent link to a well-written article that untangles Qt licensing. Thank you!

I have always found Qt licensing to be almost designed to be as confusing as possible. Unless you deal with Qt on a daily basis it could take weeks to understand what this article lays out clearly in one page. I've always considered the framework to be something "radioactive" to be avoided due to this issue.