Msn-bot is a project mainly written in ..., it's free.
Simple class for writing bots using pymsn
Simple class for writing msn bots using pymsn
The basic bot includes subscribe/unsubscribe support. Currently the subscription list is held in memory.
To write a bot extend MsnBot.Bot by providing a process method. Your process method can call send_text_message to reply to the user who sent you a message or broadcast to send a message to all subscribed users. See MyMsnBot.py for an example bot.