The IRC service has been shut down due to lack of users, and required too much work to maintain it, comparing to its usage. But fear not, there is a replacement: XMPP.
You can access the chat room via the web interface at https://conference.theanarchistlibrary.org/library/ or, logged in your jabber account with your jabber client, joining the MUC (multi-user chat) room with jid library@conference.theanarchistlibrary.org