++Skype is a C++ library for skype add-on platform independent software development. It is platform independent, easy to use, and easy to extend because of the flexible library design, inspired by modern C++ design ideas. Performance is one of the goals: only compile-time polymorphism is used.
(got my attention as Kopete has a skype plugin, using dbus though a thin layer IIRC.)
It is LGPL. The last version can control Skype not only via dbus, but also via the X11 protocol.