Yes, you do.
Your server needs Java installed. You need to put the
epubcheck.jar file somewhere where it is accessible, such as
/opt/epubcheck/epubcheck.jar. In this example, the command to run EpubCheck (
wp-config.php ) will be:
/usr/bin/java -jar /opt/epubcheck/epubcheck.jar
If you run:
/usr/bin/java -jar /opt/epubcheck/epubcheck.jar -help
You should see:
When running this tool, the first argument should be the name (with the path)
of the file to check.
If your server does not support Java, you can bypass the requirement by putting this code in a file (say,
epub.php) in your
add_filter( 'pb_epub_has_dependencies', '__return_true' );