There's an interesting post on the Qt Blog which makes a case for how some things about licensed Qt make reverse engineering and hacking more difficult: Some of the arguments are more convincing than others. I'd be curious to know of any evidence - even anecdotal - of this stuff actually going on. Security and hacking and infosec is a serious business for sure, as is crackability of $100s-$1000s/seat licenses, but for most of us the idea that some team somewhere is waiting to pounce on my FooBar App, rip it's QML and plugins off and put out their own SuperFuBahPlus App is fairly incredible... isn't it????