It's called Sothink SWF Decompiler sir.
Sothink SWF Decompiler is a program. Uomo's Sprite Client is a client made with SWF Decompiler...
Nobody I know would put that kind of time into a project without getting anything in return. One of my friends was working on a post-apocalyptic texture pack, Fallout type thing, but he quit before he finished. He had the weapons finished and was working on the gods when he stopped. If you want put hours and hours into re-creating ROTMG sprites, go ahead, but don't think it'll be easy.
Possible, but then you'd have to re-memorize every item in the game