You need python2.4 and rdflib (see below) to use cross.

To install it, just type

  python2.4 setup.py install

To get help about the options, type

  python2.4 setup.py install --help

rdflib
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rdflib can be downloaded from http://rdflib.net/ .
I use rdflib 2.2.1, but previous versions might work as well.