In your discussion about the creative common licensing, I feel strong agreement that this method indeed enhaces the sharing of konwledge. By using different types of CC licenses, knowledge are not only been protected, but also can be shared with the others, and attributes to other’s achievement in a legal and non-commercial way. I really like your example of imagine yourself as an instructor who are giving an economic course. You can use CC BY-SA license and find the resources you need, and you can then modify your those resources and use them to facilitate your teaching without any commercial use. I am sure you can fully understand the meaning behind those license, and have a carefully usage toward the OER in the future.