Irclibcc is another c++ irc-library currently under development. The goal of the project is to keep it simple but usable and fast. You can use this lib eg. for coding your own irc client or bot.
The network-communication part is based on rfc1459 (IRC protocol specification).
The Project was built in need of some network experience with C++. Meanwhile a more or less complex Bot is built on top of the library (cxBot). It is generally used for functionality testing.
It is currently developed under SuSE Linux 9.1; therefore it should work on most other Unixes.