cl-irc is a Common Lisp IRC client library that features (partial) DCC, CTCP and all relevant commands from the IRC RFCs (RFC2810, RFC2811 and RFC2812). It uses ASDF and has been tested on SBCL but should work for other implementations with extra code due to its use of usocket for portable sockets access.
The code is released under an MIT-style license. I need to mention that Jochen Schmidt laid the groundwork for this library with his Weird-IRC IRC client and that therefore some of the code is copyright him.
These details are provided for information only. No information here is legal advice and should not be used as such.