Q:

License details in languages other than English (American)

I am adding support to allow the use of GUI languages other than English (American) with a large GPL project that uses some MIT/3-Clause BSD libraries and I was wondering whether I should produce localised versions of the licences of those third party items so that non-English users understand the details of what they can do with the product.   I am aware from the FSF themselves that only English versions of the GPL are considered to be official but does the same apply to those other licences - and if not where can I get known good translations? 
I note that the Free Software Federation's French language page only has links to English versions of those licences. 
Given that the libraries that are being used in my product came with English language licence texts I suppose I have to retain the text exactly as given {or see if there are other language versions with identical functionality and version numbers} but I do wonder how non-English speakers comprehend the details of the licensing of FLOSS application/libraries when they have to use licences written in a language that is not their native tongue... on the other hand I suspect that many of the main-stream coding languages have a bias towards a part of the World that was quite happy to use just an ASCII character encoding (although that perception may also be due an observation bias on my part)! 

A:

The terms of these licenses generally require you to provide the copyright notice and license terms that you received.  They will be in English language, so you will have to use the English-language terms even for non-English users. 
Translations of the licenses may be helpful for understanding, but are not a legally relevant document.  If an official translation exists you could additionally link to that.  You should not write or commission a translation of your own.  That exposes you to unnecessarily liability if you mistranslate something, and it may actually violate the license of the license.  E.g. in the GPL v3:

Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. 

A translation would be a derivative work, and not a verbatim copy. 
A notable license family with official translations is CC 4.0 which translates the same text into multiple languages, and the CC ported licenses which translate the ideas of the license into the legal context of a particular jurisdiction, with the license then being written in the language of that jurisdiction. 
Language barriers are an important problem: how can a user exercise their freedoms to use free software when they can't read the license?  However, licenses are legal documents that need to be unambiguous and precise.  I cannot with good conscience agree to an English license if that means I also agree to a Chinese text which I cannot read.  On balance, it is better and safer if the license is expressed as a single document, even though that means some users will not be aware of their rights. 
Note that most open-source licenses are copyright-based.  They do not restrict users, but only grant additional permissions that would otherwise be forbidden by copyright laws.  The GPL v3 states explicitly: “You are not required to accept this License in order to receive or run a copy of the Program.”  So as far as these licenses are concerned, you do not have to ask users to agree to the license of your software, but only inform users that these licenses apply. 
If you do business in a jurisdiction, local laws may require you to state your terms in an official language of that jurisdiction.  How that meshes with open source licenses may be an interesting legal question, but would be a matter for local lawyers.