System tray program to keep a history of the system buffer which is called pasteboard in OS X.
To try the pre-release version you can download the binary and run it from the terminal:
./pasteboard
You'll see a system tray icon 'Pb'. By clicking on it, it will show a list of buffers. The maximum buffers amount is 20 for now. Clicking on a buffer makes it active so you can paste it.
To stop using it in the terminal window run Cmd+C to stop the process. You're done.