It's that time of the year again!
Oh... wait... perhaps I should have been more clear: it's that time of the year again when I actually log in to the forums, notice that they are hopelessly outdated, and attempt to upgrade them to the latest & greatest version, and anxiously expecting that no-one noticed that they were down for upgrade during a few minutes...
I personally do not see any significant differences, so I installed a few more language packs. If you click on the downwards arrow where your name & avatar is (somewhere to the top and the right), you should have an option for the User Control Panel. From here, navigate to Board Preferences > Edit global settings, and on the dropdown marked My language: you may select a different language, and, after clicking on the Submit button, you should see the whole forum switching to that language.
Well... just remember that the posts will not be automatically translated, of course! I know... this ought to be obvious for most... but I think it doesn't hurt to repeat it. Suggestions about new languages are welcome; you can see a list of the supported ones here (at the time of writing, these forums are running version 3.3.0, so some languages may not have been upgraded yet...)