Just an idea of mine. There are a lot of programs which have numerous languages, meaning I can switch to (interface will be translated) any of them in one-click. Most of the time the reason for this is that original translation is in a text or other text-like or simply open format. For instance, in FTRush (the best ftp client), all translations are in /languages/ format. What it means is that people can easily submit translations they made to developers. It's a win/win thing really, since 1. if a developer doesnt like or want to accept (include it programs distributive) a translation, author can simply enjoy it (the translation he/she made) himself 2. anyone can make a translation for him/her -self and use it.
Any chance this could be implemented in ArtRage? I mean, I personally could't care less about this feature since I'm fluent in English and thus I have no problems whatsoever with using ArtRage without any language-related additions. BUT I can bet my bottom a lot of people who aren't fluent would be THRILLED to have AR in their own language. And again, keep in mind, I'm only talking about translating the whole interface and not help files (that would require WAY too much effort).
So anyhow, I really do think such a change could potentially result in a lot more sales and more satisfied people. So having translations in a text-like format OR making a utility (in case you want in in a custom format) using which one is able to generate & alter existing translations would simply be a kicker for both you and your users community!
Well, just my 2 cents
All the best,
P.S. I personally would contribute at least 1 translation!