The server name is specified in the config file so that the RSS side of things works properly – you have to have absolute URIs for valid RSS output. Individual page links, resources etc., are all relative.
For example, if you look at the constructor for the WikiPage.class script library you will see that the db path is computed at run-time.
In the forthcoming release, changing the host details in the config document will automatically update all references to that value, so migrations will be simple with regards the RSS feed.