Hi and welcome, Gunivortus!
You can certainly use Program O with any, or even all, of the languages you've mentioned. You should also be able to use them together, if you like. The only real "problem" with that is that there aren't many AIML files already in existence in German, and I don't know of any
that are written in Dutch, so it's likely that you'll either have to translate some English AIML files into German and/or Dutch, or write your own. Liz has made a Wordpress plugin for Program O (there is a link to it in the Program O blog somewhere), so incorporating Program O into WP isn't hard.
Hope this helps.