To install from a fresh svn checkout, run the following:

aclocal
autoconf
automake -a

./configure --prefix=${DIFXROOT}
make
# (su root?)
make install

After an svn update, these steps do not need to be rerun.  usually just 
"make" will update everything properly, but sometimes it is necessary
to run "autoreconf" before compiling again.  If that doesn't work,
one can always fall back on the above sequence of commands.

A make install will copy libraries into <prefix>/lib/python .  Make sure this
path is included in your PYTHONPATH.