Interesting article on Qt Licensing, what does it mean for Lazarus developers?

[vfclists]

Original Article - Do Not Sign the Qt License Agreement Unchanged

Hacker News Discussion - https://news.ycombinator.com/item?id=41558799

What is the exact license under which Lazarus uses QT?

Is it LGPL with linking exception or something along those lines?

[dbannon]

In the bindings dir of Qt6 we find COPYING.TXT, "it applies to the Free Pascal Qt6 Binding". It says -

The source code of the Free Pascal Qt6 binding is
distributed under the GNU Lesser General Public License
(see http://www.gnu.org/licenses/lgpl.txt and below) with the following modification:

As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an ....

As I understand it, that requires the publication of the bindings, and that happens. It probably requires publication of changes you might make to the bindings ....

A programmer, linking to the Qt libraries using the bindings has permission to do so by virtue of the "special exception".  Making direct calls to the libraries (ie skipping the bindings) is also fine.

Interestingly, the C source code itself (used to build the libQt6pas library) has a copyright statement -
Copyright (c) 2005-2013 by Jan Van hijfte
//
//  See the included file COPYING.TXT for details about the copyright.

There is no COPYING.TXT file in the C Source dir, I assume the one above that dir is being referred to ?

That is my opinion, worth very little I assure you !

Davo

[Thaddy]

You are confusing copyright with license. The two have nothing to do with eachother, although the copyright holder may be mentioned in the license as the license grantee, but that is about it:
You can not license without holding the copyright, but which license, if any, does not matter for the copyright.
If you write original code for your self (not for your boss), you initially always hold the copyright, unless you waver the copyright. As copyright holder you may decide on a license or refrain from licensing.
When you use third-party licensed code you must adhere to what those licenses tell you, which may imply that your derived work carries one or more licenses.
Copyright sec comes only into play if somebody deletes it and claims a work as his/her own.
You can then use the original copyright to legally challenge the offender. This happens often in US patent cases, where patents are granted based on false information/prior knowledge. Usually the patents are then withdrawn, but at considerable legal costs. I was once involved in such a case and my employer had to pay a six figure sum in legal fees which took ages to recoup after we won.
Note that wavering copyright does not mean somebody else can re-copyright it. It only means you do not have to mention original source.