Yeah, I know the guy who wrote it.
>which let you fast walk
No, it let you work around having a high latency dialup connection. All it did was watch for outgoing movement request packets and respond to them with OKs. The server was still checking though. So if you tried to move somewhere you couldn't, your client would see the OK from UOE, then later see the "nope" from the server and you would rebound back to where you were, and you would often get your client's idea of your position desynced from the servers, which was the one that actually mattered.
>You could dye items glitched out colors, because the server didn't check that you chose a valid color from the dialog
Yes, there were many bugs. Large and complex software has bugs. That bug was fixed. Which demonstrates exactly my point, that you can in fact do everything server side.
>You could reveal hidden people, because the server just tagged them with a "hidden" flag, instead of not sending their location at all.
Which packet sets the "hidden" flag again? http://necrotoolz.sourceforge.net/kairpacketguide/