Menu bar on OS X is incorrectly part of the window
On OS X, menubar should be part of the menu on the very top of the screen that is outside of the window of any app. It should not be part of the application window.
In Datovka on OS X, the menu bar is unfortunately part of the main window.
Apart from being a poor interface inconsistent with the platform UI conventions (and HIG), this has also functional implications e.g. for VoiceOver users, who cannot reach the menu bar with standard VO-M shortcut (which expect menu bar to not be part of the window).