With the exception of the link on
https://openacs.org/community/ all links to the #openacs channel explicitly say that _only_ Mozilla users with a _complete_ install can use the direct link. Users with other browsers are instructed to open their favorite IRC client and connect to the irc.freenode.net server. Then join the #openacs channel.
Links to IRC.org to find a suitable IRC client and a short IRC primer at IRChelp.org are provided.
Ben, you'll find the same instructions at the top of this thread as well as https://openacs.org/irc/. Hope to see you at #openacs soon.
/Bart