Duping/Multiboxing?

Well I'm just an average joe in the game, I can't afford 8/8 characters and 16 UBHPs but I can certainly get an Acclaim or Acrop. I was just wondering if there are any currently working multiboxing or duping clients?

Actually both still exist but you will most likely have to pay for them.

What exactly is a 'dupe client'?

Dupe clients don't exist. Duping exists and there is a public but very shitty method.
Multiboxing has many different methods a lot of which are free on this site.