When you set up a Project to be shared via a browser with third parties you now have the option to restrict access by email address. This is an alternate to simply adding a password, or leaving open to all.
Now when users click on the link you send them they will have to enter their email address. On submission the system will check whether they have been set up as a Glasnost user AND if they have been linked to the project in question. If so it will let them in.
The advantage of this is that when they download documents this will be recorded and be available for you to view within the Projects module.
So you can restrict access to sensitive documents without having to bother users with a password, and keep track of who has viewed what.