As @Liebranca said:
A launcher is a .exe made with blender. The launcher is used to start your game.blend. So create a blend, use either python or bricks to start yourgame.blend and build a .exe of it.
Now the new created blend(launcher) is bound to gpl (due to the .exe is build from that blend) but your gamefile is now not bound to gpl, because any blend that is not used to create a .exe is completely yours.
launchers are pretty simple, it just launches your game.blend.
if you need a launcher with some game settings then i got one here.