You can do fine without a theme-settings.php
in your subtheme, unless you need to customize the theme settings form. I noticed the entry in the README file too, and I think it refers either to a previous version of the Foundation theme or to a next proposed feature.
If you don't need to customize your subtheme settings form you can happily proceed. If you do - or will in the future-, you can provide your own theme-settings.php; just be aware of issue #943212 in Drupal queue. You can find a neat workaround to that issue in Zen theme starterkit's theme-settings.php
.