Having had a bit to ponder I think I may just redo my instructions and make it so dnsmasq is pushed from 53 to port 54.
54, Assigned, Xerox Network Systems (XNS) Clearinghouse (Name Server). Despite this port being assigned by IANA, the service is meant to work on SPP (ancestor of IPX/SPX), instead of TCP/IP.
While this is an assigned port, its likelihood of being used is low.
mDNS on 5353 is much more likely to be used and thus really should be avoided.
5353 Assigned Yes Multicast DNS (mDNS)
Port 8080 for the web interface for AGH is acceptable as Luci runs on port 80 and SSL on 443. Unless anyone has modified their OpenWrt install, 8080 should be free. If they have, then the nginx reverse proxy method will make the AGH interface available instead.
I will also make it clearer in my instructions that ports can be changed if required but point out there are assigned ports you should avoid as they are either assigned services or reserved and as a rule you should not use ports that are actively used for other services.
(edit) My thread and wiki now updated with port 54 instead and updated pictures for rDNS as well as info about reserved ports.