ep_doi Adds support to linkify doi: identifiers in etherpad lite.
ep_html_export_using... Exports HTML using client-side routines, including the ability to use client-side filters in the export routine so you only have to write them once (e.g. if you have a client-side filter that hooks into aceGetFilterStack or aceCreateDomLine, you can add those hooks to the server-side as well by adding to ep.json)
ep_pubmed Adds support to linkify pubmed: identifiers in etherpad lite.
ep_sotauth Hooks into etherpad lite auth to trust that whatever user is set in the X-Forwarded-User HTTP header is an authorised and authenticated user. This is useful when running behind a reverse proxy that handles authentication (such as when using Apache with Shibboleth authentication).