I extracted all language files for en_US now myself. If anybody is interested, I can upload it (if you tell me where to upload it).
Currently I do the translation for de_DE this way myself, using community strings also - I can upload this when I finished, too. But this would not be compatible with the community translation generator, because I've all not translated strings in English in it. For me that's very good - everytime I see one not yet translated text in the blesta interface, I can go into the files, looking where it is exactly and change it there. And do a big search & replace for some strings... (many of them are really redundant)