A while ago I actually tried doing something like that (in C#) and so far I got it to authenticate and send private messages (none are relayed though). It actually took me two server processes running on different ports (directory and chat) to get my PoC working with the chat control.
I’m all in for an MSN Chat revival, as even though I never used it during its run, it still looks a bit interesting to me (protocol-wise and its interface). Also the whole “chat control being ActiveX” thing does really get in the way of properly introducing MSN Chat to a modern audience. Maybe it could just stay in the realm of that old MSN 4.x add-on, but I feel MSN Chat has more potential outside of an extension for an outdated version of MSN Messenger.
While introducing original MSN Chat might be difficult, @Floobby, a friend of mine, has been working on a service based off of MSN Chat named Snailscape. It’s goal is to reintroduce MSN Chat (or more generally, old chatrooms) to the modern world by making it compatible with old and new browsers (HTML and JavaScript hackery) alongside introducing more social features while still having that old MSN look and feel. It’s still under flux in terms of the chat applet and site (the chat applet is just qwebirc atm) but I believe if we have the right people, it could become more attractive and reach its goal. Also right now it doesn’t have any specific features and is just a simple IRC chat, but the creator and I have plans to change that.
If you’re interested, the site’s at http://chat.snailscape.com