Carmack on Pure Servers

Kenn Hwang sent id Software's lead programmer, John Carmack a question regarding the use of DLLs and QVMs for UI mods such as ArenaSpy. Here's the Q&A session:

FS: GameSpy's "ArenaSpy" mod is a modified dll, but it's allowed on a pure >server. Is this because it's only a UI/menu change and not an in-engine game modification?John Carmack:You can start with a dll ui, because pure doesn't get set until you connect to a server. Any loads after that will be pure.