[samiv]

It's double licensed. The Qt Company offers both a commercial and LGPL license but they do their best to bury and hide the LGPL option and use dark patterns to try to trick one to get the commercial license. They also want to push you towards getting an account with them for the installer.

That being said the packages (without online installer) are also available for direct download when you know where to look... [see link below]

If you're on Linux though the situation is much simpler since your distribution most likely already packages the Qt libs so you just use your package manager to install them and off you go...

Regardless, for anyone looking for a native portable toolkit, I don't really think there's anything that comes close to Qt in terms of functionality and tooling (like Qt Creator and Qt Designer) and once you get over the idiosyncrasies and quirks its really quite good (for the most part).

https://download.qt.io/official_releases/qt/

[sunrunner]

I'm on macOS a lot of the time so I did get to the installer part and immediately stopped as it felt like LGPL-licensed software should be accessible without needing an account, an installer (is it useful?) or anything except allowing the end user to access libraries and headers directly.

[samiv]

For the developer that knows what they're doing the installer is not absolutely necessary, you can just download the zip (or tar.gz) and extract the whole thing somewhere and go from there. The installer does provide some more advanced features such as selecting feature by feature and version by version which Qt components you want to install. At least this is how it works on Windows, I expect Mac to behave similarly.

For the end user of your product you'd of course package your software with the Qt libs (or integrate the Qt installation process in your application installation process) so that the end user doesn't need to know nor care about Qt installation at all.