Hi Matt
We did some work a few years ago with a multi-language interface for an application that was used globally.
The programming language that BiaB is developed in supports 'Resource Strings', and I believe this is the tool that they would use also.
In our application, we added resource strings directly, which added translated strings to a Translation Repository, or conversely retrieved strings from the Translation Repository.
However, we needed to have personnel who could translate 'special terminology' command actions into the languages we required, which included Chinese and Indonesian. Once the repository was established, we could build a system that included support for any of the available languages, and IIRC the end user could select which language they wished to use the system in.
I have to presume that much of the terminology used by BiaB would be somewhat specialized. I don't know if there has been manually solicited multi-language assistance from other users. Maybe
Google Translate has been helpful ?