Copying other players items directly is possible through lua I believe, but I doubt someone's going to tell you how to do it. People who make multiplayer compatible, custom items spend a lot of time doing so, and making/giving out something like this would just put their hard work to waste.
It was deemed a while ago that there is no practical purpose for such a thing. If a server is set up properly, then all users on it will have the same mods installed, and thus have access to all the same things. Why do I get the feeling this question is all from the same person making multiple accounts hoping to find someone who will tell him...
