The purpose of NickList DLL is to add a @Window or a dialog as a child into a channel nicklist. It is usefull to make your own custom nicklists or to place elements in the nicklist.
NickList DLL also allow you to retrieve the width and the height of a specified nicklist, and it also call an event-alias when the nicklist is resized, to make customisation easier.
It can also call the mIRC's nicklist popup on your custom nicklist.