We used to amend the language files in JIRA_ROOT /atlassian-jira/WEB-INF/lib to allow for some customisation in our Jira system. This was normally done by replacing the jira-lang-en-UK- version no. .jar file in the lib directory with a pre-configured version we had amended and this worked fine upto the end of Jira 4. However, I have noticed on upgrading to Jira 5.06 that these language files are no longer present in the lib directory and I cant find any details about where they have been relocated to.