@samer (and other admins), the URL in the Docker
application.yml(?) needs to be corrected to
http://discourse.emacsconf2015.org and then rebuilt.
EDIT: Actually, thinking about it, the contents of the
latest.rss file as mentioned above is fine, so I would imagine this is a bug in Discourse. How old is the current version? Upgrading can be done in the admin panel.