For using admin.pl's option to visually see your topic tree, you need
the perl module GraphViz, which requires some libraries to be installed.
Note that the GraphViz libraries are apparently not under a license that
is strictly open-source;  IBM has some mild but nonetheless restrictive
terms about how you have to let them know if you change its code.
So if non-Free software gives you the willies, simply don't install this
module, set the topic_tree_draw constant to 0, and all will be well
except that you won't get the pretty picture.

If you leave that constant 1, you'll want to install the GraphViz perl
module and whatever it requires.  You can read its own advice on doing
that if you like.  On Debian unstable as of July 2004, we simply had to
do:

	apt-get install graphviz

and for the free monospaced font we use by default for labels, we did:

	apt-get install ttf-freefont

(You can use your own font, of course.)

