My knowledge of CANopen is very limited and I am a noob when it comes to CAN. Based Wikipedia and other articles I have read, In terms of the OSI model, CANopen is a communication protocol and device profile specification for embedded systems. CANopen implements the layers above and including the network layer.
CiA (CAN in Automation) is the organization driving canopen.
http://www.can-cia.org/can-knowledge/canopen/canopen/
Each manufacturer can define device IDs in the messages that are communicated using CANopen ( which I guess is the application layer).
A complete overview of CAN network layers is explained here:
http://www.can-cia.org/can-knowledge/