Since I'm planning to expand the use of dynamic graphics in my problems, I agree that libgd-gd2 is "an important component". (I would like to know a way to increase font size for a label in a graph: http://webwork.maa.org/moodle/mod/forum/discuss.php?d=2623)
I suspect libgd2-noxpm was used for a fresh install of Ubuntu 11.10 Server because Xwindows is not part of the default configuration of an Ubuntu server. I did find a discussion "-xpm or -noxpm" from 2006-2007 at http://forum.soft32.com/linux2/xpm-noxpm-ftopict232577.html
FWIW: the only optional modules I chose during this setup were OpenSSH and LAMP.
minor glitches with Ubuntu 11.10 Server and WeBWorK 2.4.9
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