Remix this project, then delete the watermark sprite (the thank you at the top left). Also, feel free to copy the script! Make sure you put this on all sprites you want affected. Rename the variable something that blends in with any other variable. PLEASE SEE INSIDE AND READ THE COMMENTS.
This is based on the expected first reaction to watermarks; deleting it. This is not 100% foolproof, there are other ways around this, which can't be fixed through any code, even the most complex. If they do delete the watermark, they will not know how to fix it, as this will not be the obvious explanation (if you've covered the scripts up with random code). Hopefully, if they don't see the variable, they will give up.
