Hey Chas,
Welcome to the forum, and thank you for becoming a Yummy FTP user!

I will try to get the wiki updated as soon as possible. In the meantime, here are the functions of those two preferences:
Active IP Address
This allows you to specify the IP address to send to the server when using Active Mode FTP. It works around some problematic NAT routers. If you don't use Active Mode FTP and don't have a problematic NAT router then you don't need this option
Export passowords in URLS
When you choose 'Copy As URL' from the File menu or context menu to get a fully qualified url ready for pasting elsewhere, this option allows you to include the password, or not. If the password is not included then using the url will require the end user to enter the password. Other wise the url can be used without any authentication by the end user