The basic structure of a XOOPS theme is similar to that of any other static website template. The primary difference is the addition of Smarty variables that interact with XOOPS to output your dynamic content.
If I set up an articles module and have this only available for 'webmasters' to access, set via the admin panel and say one other group called 'elite' for instance. Would the contents that are included in this module be accessible and spidered by the search engines as normal?