AFAIK, French, German and Hungarian versions, in addition to Polish, are regularly updated.
French versions of WinUAE are usually announced and links provided on EmuNova:
http://www.emunova.net/news/
There are even French versions of the beta releases!
http://www.tradu-france.com/
I'm no longer sure where to find the German and Hungarian versions, sorry.
You are correct; the non-English language versions are produced by editing the translation.dll available from winuae.net with each new version.