title: Chrome Extension Licensing System
body: <p>I am currently developing a chrome extension and need to make sure it will only be run as 1 instance per license key. Basically, I am planning on selling the extension in limited amounts online and providing customers with a license key upon purchase. How can I ensure that the extension is only running on one computer at a time (sharing of license keys is against our terms of service)? I need to be as sure as possible that the extension cannot be cracked but am at a loss for the simplest way to do this.</p>
  
  <p>Thanks!</p>