Jabberoo is an object-oriented, cross-platform C++ library which provides handling logic for the Jabber protocol.
Jabberoo uses (hence, requires) libsigc++ to provide typesafe event notification. You will need to get and install libsigc++ before you can build jabberoo.
This site used to have links to horribly outdated versions of Jabberoo. More recent versions are available from JabberStudio, probably in the Gabber project.
Unfortunately, it is no longer maintained.