There is an option to create a Login Handler based on an external MySQL database (it has options to specify all the data/fields needed). The forum will load the data from it and, based on how it's setup, create/sync accounts on the forums.
You can take a look at it on your site to verify how it works. Here's a link to the guide:
If that won't work, or if your friend needs something different, creating a custom Login Handler is also an option.