I wonder if you can use the WoTLK Classic client to connect to this. IIRC there was a project to proxy WoW Classic client connections to server emulators like these.
It might prove more challenging than one might expect, because the Classic clients are actually modern WoW clients patched to behave like the originals. Blizzard apparently evaluated using the original clients, but found that differences in server architecture and lack of security patches made that impractical.