IRCDs

ircd

The original ircd. This daemon is used on IRCnet.

http://www.irc.org/servers.html

ircd-ratbox

ircd-ratbox is the primary ircd used on EFNet, combining the stability of an ircd required for a large production network together with a rich set of features making it suitable for use on smaller networks.

https://www.ratbox.org

ircd-seven

Freenode's IRC daemon.

https://github.com/freenode/ircd-seven