Wait a minute, is the shot above live from the satellite? Is the satellite that far out?! To be able to get a shot of the earth in its entirety, you would have to be pretty far out.
If the terminator line means when it is half light and half dark equally in the north and south hemispheres, then yes it will occur twice a year. Spring equinox and fall equinox, since the sat is always above the equator and at the spring/fall equinoxes the sun is also above the equator, the dark/light line will go from north pole to south pole.