It was intended that the status applet be available to all users.
When you launch the Update Manager, it will require you to provide credentials to use the application (these credentials are typically username and password of an account that has root priviledge) .
If a user has such credentials, anything that they could do from UM, they could do from the command line, so perhaps I am missing the issue....
The ability to make this readily configurable system wide is on our future feature list. For now you can easily disable this feature for all users by either removing the file /usr/dt/config/Xsession.d/1001.swupnot or editing this file to comment out the one line that starts /usr/bin/swupnot
-Dave