This is the complete download for Jailbreak 2004c (aka. Service Pack 3). It can be used for completely new installations or to upgrade any previous version of Jailbreak 2004.
This 7z archive contains a UT4MOD installer. Extract it to any place you like, then run it to upgrade your Jailbreak installation. If you can't run UT4MOD files, either get the plain archive version of the patch, or use UT2Kx Regcheck to fix the file association.