Thanks for your feedback. I am currently working to redo the entire documentation with videos, write-ups and examples. A lot of what you said makes sense, and I am sure future releases can make this feature a lot more user-friendly and intuitive.
Also, it is up to the end-user to use this feature responsibly. Scripts cannot be ‘stolen’ if they are freely provided as open source (e.g. with a GPL, MIT or BSD license). Copyrights are kept intact because these scripts often have the script author in the header, which is often stipulated by the license.
Again, the end-user must adhere to the licensing for scripts hosted on CDNs and make sure there is compliance before using the External Script feature.
Anyway, I appreciate what you have said and will add some of these ideas to the tasks list for future developments.