Report About Using Free QtCertification without open source.
I've Checked This product is [https://www.4kdownload.com/ko/products/product-videodownloader] using Qt LPGL v3 License. But Can't See Any Guide of Product Source Code. Could you Check it out?
Thanks for the heads up. As it is LGPL v3, they should provide a way for you to get the right Qt version and toolset to change the Qt version underneath the product.
The tool source itself does not have to be opened (that would be required if they used GPL).
However if they are missing the information on how to obtain the correct Qt version and guidelines on how to change the Qt libraries in the product, they are breaching the LGPL license.
Really? Then That Product is not illegal of This Section?
"Must make a Qt source code copy available for customers"
That's Qt's source, not the software.
The GNU Project has two principal licenses to use for libraries. One is the GNU Lesser GPL; the other is the ordinary GNU GPL. The choice of license makes a big difference: using the Lesser GPL permits use of the library in proprietary programs; using the ordinary GPL for a library makes it available only for free programs.