JSPWiki doesn't always detect the preferred language from the browser. The intended behaviour is that if there is no user-pref cookie, the language setting should follow the language of the browser.
This is a collection of facts from several mails on the list.
I've got a personal wiki installed on Tomcat 6, which runs without this problem. This installation (v2.7.0-alpha-9) has been upgraded successively from 2.6.
I've deployed the JSPWiki v2.7.0-alpha-9 on a Glassfish 2ur2 server and get English as the default language for a not yet configured browser (without JSPWiki cookies), although it is set to select de-de as primary language. It's the same with Firefox 3 and IE 7.
However, switching to german language in the user preferences works.
Yup, just checked. It works on 2.6.3, but not on any 2.8 alpha releases.
I tested against v2.7.0-svn-44 <http://zwiki.rabobank.nl/rss.rdf>, it doesn't work there.
I checked the source of the latest version, could not find anything reading the Language header, just reading the cookie contents (mainly Preferences class).
Some additional testing (all with FF3 on XP) confirm the same results as Janne :
v2.7.0-svn-44 ==> doesn't work
v2.7.0-alpha-9 ==> doesn't work
2.6.3-rc-2 ==> works