From when qt is a commercial application?
If u go here, http://qt.digia.com/Product/Developer-Tools/
and try to download qt, it says about a 30 day trial..
Lucky me if i go here (http://qt-project.org/downloads), it is free. What happened here, i am confused..
So what if i want to sell the application i made with qt, i must have made the application with the commercial qt?
and if yes how much does the commercial one costs?
As long as you conform with LGPL or GPL Qt is free of charge to use.
If you need static linking or support there is a commescial option from digia.
Nothing has changed in that regard to times when Nokia was in charge.
As unai_i pointed out, you have 3 licensing choices: LGPL, GPL, commercial. When buying commercial, you have the freedom to choose any license you want, you get support from Digia, Commercial SDK and some more goodies + you help in financing Qt project.
If you choose OS licences instead, you just need to conform to those licenses. They both allow you to sell your application. LGPL and GPL are not about money, they are about source code freedom.
LGPL allows you to choose any license for your application, but you are required to publish any changes you do to stock Qt + your app needs to work with official Qt builds.
GPL forces you to license your code using GPL, and to publish it.