Hi,
I tried to work with another language than english. I found that no matter which language user set in its account, because it should be taken from a request (from browser). I tried this but with no results :-(.
I made a little investigation and found that only english language is accepted. The reason is (I think so) the constructor CoreModule(boolean persistent). The only one locale which is used there is Locale.US.
When I changed the constructor to:

 public CoreModule(boolean persistent) {
 super(persistent);
 Locale locale = Locale.US;
 locales.add(locale);
 bundles.put(locale, new ResourceBundleAggregator(locale));
 // french
 locale = Locale.FRANCE;
 locales.add(locale);
 bundles.put(locale, new ResourceBundleAggregator(locale));
 }

it started and seems to be good. The french language is used.
But I found also some other problems:
1. I must use language fr_FR (french/France). "french" don't works.
2. When some texts are not translated (I think so) the code like this
${search.ADVANCED_HELP} is used.

Anyway I will try to use polish language and I hope it is going to work fine.