[pavlov]

Yes, if the language's class libraries are GPL and you're linking them into your binary, then your app has to be GPL too. That is the most common interpretation at least.

This is exactly why LGPL exists: https://en.wikipedia.org/wiki/GNU_Lesser_General_Public_Lice...

For open source class libraries, LGPL makes the most sense and is used by the vast majority of libraries in the Linux world.

Also, some libraries are GPL-licensed specifically to protect commercial interests. Under such a dual licensing scheme, you can use the free GPL version, but then your app has to be GPL as well... Or you can pay for a commercial license that lets you build closed-source apps using the library.

Qt used to have that kind of dual license, but they switched to LGPL after Nokia acquired Qt sometime around 2008.