Does @property copy in combination with readonly make sense?

You are correct, it does not make sense to have both.

According to Apple's documentation (which I've linked here for you):

copy
Specifies that a copy of the object should be used for assignment.

The previous value is sent a release message.

The copy is made by invoking the copy method. This attribute is valid only for object types, which must implement the NSCopying protocol.

So yes, you're correct... readonly creates a getter method and copy would be effectively ignored, since there's no setter method that does assignment.