I'll try,
To administer portlets for a class go to the 'Administer' page of the class's portal and choose the 'Manage Applets' link.
I think a 'subject' and 'class' are analogous to 'class' and 'object' in OOD terminology. A class is an 'instance' of a subject. For example a subject can be 'Biology 101' but there will be different classes on this subject such as 'Biology 101 - Spring 2003 - Section 002'
I don't know about the last it seems suitable for any collaborative environment.
