Adding translations
If You would like to add a translation to the Citadel, look into the game's locale/ subdirectory. There are some localization files that can be translated to the desired language - just choose one of them and translate it. The details about translating can be found in the existing translation files - they are widely commented.
While saving the translation, choose a name for it (ie. "GERMAN") - the name of the file should consist of the name of the translation and a ".loc" extension (the extension must be lowercase!), ie. "GERMAN.loc". The name of the translation will be used in the "Choose language" menu.
Second thing to do is to create apropirate fonts. If your language does not use any diacritics you can use English fonts - just copy tex/fonts/ENGLISH.far to tex/fonts/your_translation_name.far (ie, GERMAN.far). The name of the font file must be exactly the same as the name of the translation (localization file), so if the name of translation is in uppercase then the font file name must be also in uppercase (ie. GERMAN.loc and GERMAN.far or german.loc and german.far; all extensions must be in lowercase).
If your language uses diacritics then you need to create new fonts.
Download the FarEditor and open one of the existing font files (located in tex/fonts/). Extract all the TGA files that are present in the .far file and edit them. When finished, create a new .far file with fonts (ie, GERMAN.far). The name of the font file must be exactly the same as the name of the translation (localization file), so if the name of translation is in uppercase then the font file name must be also in uppercase (ie. GERMAN.loc and GERMAN.far or german.loc and german.far; all extensions must be in lowercase).
You should also remember that some of the TGA fonts should have transparent background - you can check which of them by opening one of the existing font files. To add the transparency you can use a tool that is present in the FarEditor (menu "Tools->Add transparency"; use the "Only to pixels of a given color" option and select the color of the background). You can also compress the files (also using the Tools menu) so the font file will be smller.
When writting translation use uppercase letters for basic latin alphabet and lowercase letters for diacritical signs.