Se você tentou a resposta aceita; a abordagem SIMBL TerminalCopyOnSelect, mas falhou com um diálogo mostrando:
Terminal 2.5 (v334) has not been tested with the plugin TerminalCopyOnSelect (null)(v0.1.0).
As a precaution, it has not been loaded. Please contact the plugin developer for further information.
É porque o TerminalCopyOnSelect que você baixou se aplica somente se a versão do pacote Terminal.app for 237 - 240.
Você pode fazer o download e criar você mesmo em github .
git clone https://github.com/genki/terminalcopyonselect.git
cd terminalcopyonselect
open TerminalCopyOnSelect.xcodeproj
# edit Info.plist and set SIMBLTargetApplications's MaxBundleVersion to 400, which is enough for MacOSX Yosemite's Terminal.app
# hit build, and it will copy TerminalCopyOnSelect.bundle under it's proper place: ~/Library/Application Support/SIMBL/Plugins