The text for the emails can all be found in our language files. Look in /language/xx-YY/xx-YY.com_jfbconnect.ini file (where xx-YY is your language). Look for the section with the comment "; Email Notifications for New Users" and you'll see the language strings for the different emails we send out on registration. Whether you have automatic registration enabled, activation required, etc will determine which string is used. The passwords are filled in with the %s in the string, so if you remove those from the appropriate string, that should do the trick.
-Melissa