Seriously, $14.99 for an app to do what the OS does for free? Grab is located in /Applications/Utilities. If you dont want to use Grab, use the key commands Command+Shift+3 for whole screen, Command+Shift+4 for a crosshair to select anything and finally Command+Shift+4 then Spacebar and you get a camera to take a snap of whatever it's placed over. Window, Dock, Menubar...
It produces a file with date/time and png, jpg....whatever you set it to be. If you cant get you want from those options then by all means, pay the $14.99...