You can download it from www.unrealtournament.com/ut2004/downloads.php
save it to your /tmp
extract the package in your /tmp
then cp -v -R /tmp/<ut2004-patch>/ /<ut2004-patches>/<installation path>
you can also download the Windows Bonus pack.
save it to your /tmp directory
unzip the selfextra exe file and copy that also into your UT2004 installation directory.
Good luck and let us know if you need more help.