There was a shift to a different editline library than that of Salz and Turner in Rakitzis's more recent rc. Looking at es-0.9 might you add to the documentation which editline is being referred to as an option to GNU readline.
Factually, the README does not contain information on obtaining editline, but does include an ftp link (ftp://ftp.sys.utoronto.ca/pub/es/) to where the editline.shar file may be downloaded.
Quoting an email: