They can't steal it if they can't find it!
This probably doesn't work with newer browsers since their developers continually screw things up creating more problems and call it progress.
1. Write your script.
2. Create a link in the document head section and give it an "id".
3. Load document to make sure script loads and works correctly.
4. At the bottom of the script (file) use the .removeChild(); method.
5. Reload document and see if script still works.
If not, it's because the browser version has been updated to adapt to using js and css plugins. Therby, rewriting what was initially loaded to the browser.
If it does, it's because the version your using has not included the update. Meaning the script
loads and will maintain normal processing and functionality.
6. Check your browser's "view source" to see what happens.
7. Check your cache directory to ensure script does not exist.
The DOM's "removeChild" method, in older browsers, would rewrite the HTML displayed and remove the script from the cache without affecting the processing or functionality of it. Simply because the browser had already loaded it for display. Removing it after the fact is what could be used to protect script from being stolen. But, as i said, browser developers keep screwing things up.