Re: Copyright notices on GPL'ed software

[Alfred M. Szmidt]

   What copyright notices should be left and/or added to the source.

All such notices should be left as they are.  You should add your name
(and the name of any contributor that add changes that are deemed
copyrightable unless you start collecting copyright assignments) to
the list of copyright holders.

   Previously, the 'About' box in this graphical software showed his
   name and copyright. Should this be removed (he has not in any way
   agreed to be part of the new project, left in place, or what else?

This should not be removed.  He is still the copyright holder of the
project, and it is important to note the license of the program for
users to see.  The GPL explains this in section 2 and 3.