I copied the jar/xml, renamed to jServer-11.0.20, created a folder called jserver-11.0.20 and updated the XML as required.
I downloaded Jetty 11.0.20 (the zip version) from the project website. Unzipped and copied the libraries across. NOTE the libraries are split across multiple directories in the zip file but need to be placed in the single "jserver-11.0.20" folder