If you don't mind having a cms style of front end this might work for you. I have vBulletin running as a menu link on my main site which is powered by Joomla. The joomla portion of site has google-translation running for whole site, so the vBulletin section gets translated when visitors go to the forum section where I have free puzzle magazines available for download.
Visitors must first select a language on main site for translation to work on vBulletin, which does cause problems for visitors who bookmark only the forum section, as I haven't yet found an easy and elegant and simple way to add google-translation with vBulletin.
To see how this method of translation works with vBulletin visit my
site, select a language, and choose the third menu option "Free Magazines" on left side menu panel.
Joomla is free and there is an extensive list of both commercial and free modifications. The translation I use is the free one but there is also a very inexpensive commercial version available.