tuxguitar-coreaudio is a plugin for TuxGuitar. It connects TuxGuitar’s MIDI sound output to CoreAudio. That means that with this plugin TuxGuitar will no longer use Java soundbank, but CoreAudio MIDI output.
CoreAudio is a sound output system for MacOS, which makes tuxguitar-coreaudio plugin usable only on PowerPC platform.
tuxguitar-coreaudio is included in TuxGuitar distribution for MacOS. You shouldn’t bother to install it manually, unless you downloaded wrong distribution package. :)