I have already visited this page: http://www.zenphoto.org/news/translating-tutorial/#theme-translation
Two questions remain unanswered.
– For core Zenphoto contents, the functions gettext() and ngettext() exist. For extra themes, I can use gettext_th(). Is there a similar function for plural strings?
– I only want to provide English and French. If I prepare a locale folder with a French translation, do I still need to have an empty en-US folder? If I later want to distribute my theme and, say, a German user wants to use it, will he be OK or do I need to place an empty de_DE folder?