Since Joomla 1.5 there is an easy way making translations for extensions. Here you can download a Sample Translation Package.
NOTE: This Package is a sample! Please always use the language files of the latest version of Joo!BB. Please also use the country code of the language you want to translate instead of en-GB! For example de-DE when you are making a translation into German. You need to save all translation files as UTF-8.
There are several language files have to be translated. Easy to handle is the backend translation. The frontend translation is a little bit complex because of more flexibility of Joo!BB.