Why different URLs could access the same resource?

I am a novice for the web development. Now I am running web application--CourseBuilder (an open source project developed by Google). It is used to deploy online courses. What I am running is coursebuilder 1.6 (Download)

So firstly, I run a sample course: http://ift.tt/1yQEPQj And then I use the import function to create second course which imports from the first course. http://ift.tt/1yQEOeY

I can't find the code to copy all the assets during the importing process. And also from common sense, there is no need to do that. We call share these content in multiple courses. However, when I check the get requests for both courses, it looks like the files are all from different directories. In another word, it seems like it copies all assets files into a new directory.

For example, as for the log image,

• Log image request URL for the first course:

http://ift.tt/1Gjcxpo

• Log image request URL for the second course:

http://ift.tt/1yQEQ6x

Is it true that it copies all files to a new directory? or is there any technique or trick involved? You may need to download the source code to see what happens there. I have tried to search inside the source code, but just find it does copy the course content, but can't find they copy other files, such as css files.