If you're using a staging site or localhost in addition to a live site, you can use the same license — provided the domain name is clearly a dev or staging site. This rule applies to both Direct (Freemius) and CodeCanyon purchases. Dev/staging installations don't count against your activated-site quota.
For the full, maintained list of recognized dev/staging TLDs and subdomains, see the documentation:
documentation.wpcloudplugins.com/licensing/local-staging-sites →
If your staging environment uses a domain that isn't on the list, contact our support.