Can I make all users in a project to get notifications for all comments and other project changes by email?

[Jeremy Gaudet]

Yes, you just need to create a JIRA user backed by a mailing list, and add that user to the project's notification scheme.  Or, alternately, put all of those users (by JIRA group or individually) in a role, such as the "Project Notification" role, or the "Gold" role, and put that role in the notification scheme (for all actions/notifications).  Obviously the "Project Notification" role would be more appropriate.