Modifying a Joomla! language pack

Joomla! 1.5 offers partial multi-linguality, meaning that the system language of Joomla! or its extensions can be translated, but if you want to translate your content, you’ll need third party extensions like Joom!Fish or Nooku. If you want to modify the system language, you can edit the necessary files, but with the next Joomla! upgrade, your changes might be gone. So how to deal with this? Language files in the Joomla! directory structure With Joomla!, [...]