He was referring to Minecraft Classic if you were wondering. Classic was around before there was SMP and was primarily for freebuild/creative mode with less features in current Minecraft. I used to play a lot back then, it's mostly dead nowadays. If you're interested there's a "spiritual successor" which is called Classi Cube, but it's more or less dead as well. Here's an example of Classic.
For all the nostalgics in the thread, there is a way to play MC Classic.
There's a program called Classicube that is essentially a modded Mc Classic launcher that you can download and use to play on older gamemodes like Zombies and stuff.
Yeah, classicube is good if you ever have that nostalgia fever. However, it's not very well-known, so there's usually like 10 people on all of the servers at a given time, and about 20 or 30 active servers to choose from.
For anyone interested, here's a link: https://www.classicube.net/
You can still play Minecraft Classic clone called ClassiCube, it's more or less the same game but with few additions like custom blocks, placable NPCs, support for per-server (or per-world if server supports it) texture packs and better optimization.
I made a HvZ server for Minecraft Classic a long time ago. There were already zombie tag servers but I tried to make it more HvZ-like.
If you want to do Classic, i'd suggest using the Classicube client. It has a few more features and a less empty multiplayer, as well as zero of the hassle of trying to get Java to run in-browser.
T9K uses fCraft which can be found here: http://www.fcraft.net As far as I know, WoM no longer works, everybody here at fCraft uses ClassiCube (a few of our developers also worked on this software too), the client can be found here: https://www.classicube.net .