According to TID 3604883 (old) for both iPrint on NetWare and on OES you can append the port number to the hostname/hostaddress in the gateway autoload command:
"Other ports can be used by appending :port_number to the HOSTNAME or HOSTADDRESS. For example, 188.8.131.52:9101"
On the iPrint Appliance you can specify the port number directly with the PORT= parameter. See the docs here :
www.novell.com/.../printer_config.html There is a table for the Gateway Load Parameters that explains it all.