module development questions

Just wondering why the example module in the docs explains how to make the tab.download.php file - I thought the fieldtype API would replace this? I had a look at the forum & pages modules, which both seem to add field to the publish page, but theres no tab.modulename.php file?

Also does anyone know if theres any ways for a module/extension to make use of the communicate page? Currently theres options to send to each member group, and each mailing list, but I want to be able to send to a group of email addresses listed in a specific module DB table. Doesn’t make sense building a separate mass-emailer within the module

Thanks!