z.glNavigator1 (walkingSim) - In this version of the patch (z.glNavigator1), moving forward/backward/left/right = moving parallel to the x-z plane. Moving up/down = moving along the y axis. You can look up or down while 'walking', but this will not affect your movement on the y axis. You can look around as you move up/down, but this will not affect your movement along the x and z axes. The camera and lookat behavior can be seen as, perhaps, similar to a helicopter - without roll.
z.glNavigator2 (flyingSim) - This version of the patch is a true flight simulator (i.e. with camera and lookat behavior similar to a plane - without roll). Forward/backward is in reference to wherever you are currently looking.
z.glNavigator_quad (quadFlyingSim) - This a surround-video port of z.glNavigator2. This version renders four viewports into the same GL space as you fly around, so that you can see all areas of space around you as you fly. These are (from left to right as displayed on screen): frontview, rightview, backview, leftview