The file "NoEntryHack.u" is a little counter-measure against [ELF]clocKwize's UT2003 Entry MD5 hack for Ut2003. This tool looks for disallowed files and disconnects the client if it finds any. By default the blacklist contains only Entry.dll and OpenGL32.dll, but the server admin can easily add additional files. Unlike the file blacklist in Anti TCC 2k4 v1.18 this tool will not automatically check all package folders, though.
You should use No Entry Hack in combination with Anti TCC 2k3 or UTSecure.