libpurple 3 is the current development version of the libpurple universal messenger library.
Finch 3 is the current development version of Finch Universal Messenger.
GNT 3 is the current development release of libgnt (GLib Ncurses Toolkit)
GPlugin is a plugin library for GLib based applications. purple 3 uses it for all things plugins.
Convey is tool to help you run pipelines of containers. We use it to test builds across multiple operating systems as you just need a container runtime instead of a dedicated host.