From Forum Nokia Wiki

Here is how to translate MWS localization files into a new language.

1. Find out all the _loc.py files, there is one in /htdocs/Framework and one for each web application in /htdocs/Web_Applications. Start by copying one of the file and edit your own translations to a new file. For example to create Swedish localization, you need to create mws_framework_se_loc.py file in /htdocs/Framework and similarly a _se_loc.py file for each web application.
2. Edit file /htdocs/Framework/WebFrameworkConstants.py: add your new language into two places (here Swedish is added)
   1. SUPPORTED_LANGUAGES = ('en', 'fi', 'fr', 'de', 'it', 'es','se')
   2. LANGUAGE_NAMES = {'en':'English', 'fi':'Finnish', 'fr':'French','de':'German', 'it':'Italian', 'es':'Spanish', 'se':'Swedish'}
3. That's it! Now restart the server and you should see your new language available in Settings web page.

Why not make your translation to other users? Upload it to http://mosh.nokia.com and add tags 'mymobilesite' and 'mobilewebserver'. Please also drop a note to us: https://secure.mymobilesite.net/contact/.