As far as I understand, "Eat them all" demo replicates the same AI for ghosts as in the original Pacman. You can move the ghost with any behavior your like - 8direction, Bullet, MoveTo, TileMovement. The difficult part is how to chase the player and run away from the player.
The absolute minimum I guess is this - choose Bullet direction at random with choose(0,90,180,270), move in that direction, on collision with wall choose again. Ghost will just be wondering around.