This information is from Wikipedia.
theY4Kman has worked on several major projects, and some smaller ones.
With the advent of CheatDevice by edisoncarter, the cheats created for it were spread across the web. On the GTA Forums, ADePSP and theY4Kman discussed creating a database for all the new cheats. theY4Kman wrote the website front-end for it, and hosted it on his site. It was a very basic form, consisting of an author field, a name field, a description field, and a cheat field. ADePSP wrote the desktop application for it, in Delphi. As the new database was about to be released, theY4Kman thought up the name "CheatSync."
CheatSync was a huge hit. Hundreds of users contributed thousands of cheats. The crummy front-end and buggy program couldn't deal with the load. edisoncarter purchased cheatsync.net for ADePSP. ADe programmed an online version of CheatSync, in the PHP language. At this point, theY4Kman was no longer necessary.
Zach offered to create a version of CheatSync which used AJAX, but the project quickly ended, due to lack of time.
Zach became addicted to Source games (e.g., CS:S and HL2). With his programming background, plug-ins like EventScripts and SourceMod. At first, he experimented with EventScripts. However, he did not appreciate the lack of performance it held and its heavily scripted language. This led to his delving into SourceMod.
Upon learning SourcePawn (The language of SourceMod, based off Pawn), theY4Kman wrote the plug-in "Maplister." It was a very simple program, that printed out all the maps available on a Source game server. After his first plug-in, he developed a few more plug-ins, such as Weapon Rewards Advanced, CommandReact, UserRestrict, and EventInfo. His latest plug-in is Triggers, which provides commandlist.txt functionality to SourceMod users.
One of his latest projects is an extension of SourceMod. Viper is a program written in C++, which allows SourceMod developers to code plug-ins with Python, instead of SM's native language, SourcePawn.
The project took off the in IRC channel #sourcemod. One of the members bet theY4Kman that he couldn't do it. However, Viper is being actively developed now.
Originally, Viper was named "SMPython," for "SourceMod Python." To Zach, though, it seemed very generic. A week or so after the title "SMPython" was given, the project was renamed to "Viper." The new name came from the snake family and the user "Viper," who is an active member of #sourcemod.
theY4Kman means "the year 4000 man." The simplification of "Year 4000" to Y4K was derived from "Y2K", meaning "Year 2000". Thus, Y4K is actually pronounced "Why Four Kay," not "Yak." This common mistake originates from the notion that frequent internet users speak Leetspeak. However, using "Yak" is accepted.