You can customise the language of the interface using a language file. Note that the method templates are not translated using this file, just the program interface.
From version 2.2.1, Community Edition uses a new, richer language file format, the same format as used in our other products. It is a text file that can be edited with our special Translation Tool, or directly with a text editor.
Download the current set of language files: Translations and Locale