http://tinyurl.com/spectro-aras-eng
I have not tried it but I expect it could be made to work the other way as well, translating everything into French
Note, it has a couple of limitations:
It tries to translate the English posts into English too so it sometimes makes them look a bit odd
You cannot post directly from the translated version. If you try, it takes you to the original version where you can submit your post
Cheers
Robin