Following the usual untar of the aolserver3.3ad13 sources you should cd to the root/aolserver directory. What's puzzling of course is that the excerpt you've included apparently shows that you are in that directory.

Here's what I just tried, and it seems to work for me. I don't really know what to suggest, except to ensure that you're in the right directory, and have the right patch file (mine shows a length of 240840 bytes.) (and perhaps to play with that "5" (in the p5)). Perhaps someone else can explain differences or problems with patch....?

[nsadmin@web p0rn]# cd /tmp
[nsadmin@web aolserver]# ls -l /web/tag/download/AOLserverVirtualHostingPatches/13.file 
-rw-r--r--   1 theasher web        240840 Sep 19 04:28 /web/tag/download/AOLserverVirtualHostingPatches/13.file
[nsadmin@web aolserver]# 
[nsadmin@web /tmp]# tar zxvf aol/aolserver33.ad13.src.tar.gz 
root/
root/aolserver/
root/aolserver/doc/
  .  .  . 
root/arsdigita-aol3/make-dist.sh
root/arsdigita-aol3/make-src-dist.sh
[nsadmin@web /tmp]# cd root/aolserver/
[nsadmin@web aolserver]# ls -F
ChangeLog	    DISTRIBUTION.txt  Makefile	doc/		   include/    nscgi/  nsd/    nslog/	nspd/	 nssock/  nsvhr/    tcl/     tcl8.3.2/	thread/  windows-nsd.tcl
DISTRIBUTION.patch  LICENSE.txt       README	encoding-doc.html  index.html  nscp/   nsext/  nsodbc/	nsperm/  nsunix/  scripts/  tcl7.6/  tests/	win32/
[nsadmin@web aolserver]# patch -p5 </web/tag/download/AOLserverVirtualHostingPatches/13.file 
patching file `ChangeLog'
patching file `Makefile'
patching file `include/ns.h'
patching file `nsd/config.c'
patching file `nsd/conn.c'
patching file `nsd/dbinit.c'
patching file `nsd/dbtcl.c'
patching file `nsd/drv.c'
patching file `nsd/log.c'
patching file `nsd/nsconf.c'
patching file `nsd/nsconf.h'
patching file `nsd/nsd.h'
patching file `nsd/request.c'
patching file `nsd/serv.c'
patching file `nsd/tclcmds.c'
patching file `nslog/nslog.c'
patching file `nssock/sock.cpp'
patching file `nsunix/nsunix.c'
patching file `nsvhr/nsvhr.c'
patching file `nsvhr/nsvhr.html'
patching file `tcl/form.tcl'
[nsadmin@web aolserver]#