I've thought several times about OpenACS internationalization. It would be great to see it happenning.
Don has mentioned that he has done some work on that area for the greenpeace work he's doing. Henry has done some work too. Now Emanuelle. Perhaps it's time we create an OpenACS-i18n forum just do discuss i18n and make it happen, and happen right.
I can see the having one .adp template per language, with a different ad_page_contract call (this was the approach Don used IIRC), but what about the messages sent from the .tcl files? One way would be to go with gettext: http://www.gnu.org/manual/gettext/html_chapter/gettext_13.html#SEC210
