Papercarbonate is still a work in progress and isn't yet available for download.
This subproject's goal is to condense down and imitate several aspects of the user interface (UI) from Lidslate. It's named after the material polycarbonate, and 'paper' since it's just meant to be a PDF/paper demo of the actual Polycarbonate shell.
Since the full Lidslate OS can't run on the iPad or other devices like locked phones and non-PC tablets, this is a side project of love made by the same author who makes the Lidslate project.