Instead of individuals providing paid language apps, why doesn't Boonex offer a Pro subscription to the folk who create language apps for as long as they maintain them? That way UNA will be quickly available to international markets which will help it grow. Personally I haven't seen another app which charges for language packs and it just seems tacky to me.
I used to maintain the Brazilian Portuguese translations of a number of Joomla apps for RSJoomla! (until they stopped translating them) and in return they gave me free subscriptions to those products. It was a win-win situation all around.