Well, while this is mostly true, near the edges (as seen from Earth),
libration does allow some small rising and setting action.  This is because the
Moon is not locked firmly in place, but wobbles slowly back and forth a small
amount.  Here is an actual set of photos assembled into an animation of the
effect:    http://www.theman.themoon.co.uk/librations/
    The effect can be up to about 8 degrees of latitude or longitude.  This
movement is a leftover from when the Moon had an actual day and night.  It lost
this motion long ago due to tidal influence from the Earth, but it didn't come
to a dead stop.  So even today, many millions of years later, the Moon still
undergoes periodic rocking in both latitude and longitude.
    So a colony placed on the visual terminator line of the Moon could indeed
see the Earth rise and set as much as 16 degrees or more.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip

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