What does this feature do?
What makes this feature interesting? Traq is really good for debugging website, for keeping a task list of projects, clients and general administration. For my use, most of this data is sensitive and we would want to keep it internal. I think the option to protect traq behind a login will really add value to the system.
If you edit the config file, there is an option to require login. There is also an option in the AdminCP on the Settings page to disallow registration.