PostBooks distributes their schema as a Postgres binary dump file for
use with pg_restore
They are available for download here (not in the source tarball):
http://sourceforge.net/projects/postbooks/files/03%20PostBooks-databases/4.1.0/
Is this format suitable for making a source package or do we need to
load it into Postgres and then pg_dump it again as text / SQL?
I would prefer to simply distribute the original files so that people
can compare with upstream's checksums if they wish.