Each script can be added to as many pages as you want, given they all are on the same root domain (subdomains of a root domain are allowed).
Adding the script on multiple websites (different root domains) is however not allowed.
To add the script on multiple websites, you can request our team at firstname.lastname@example.org and we can add multiple sites in your existing dashboard. Each website though will be on a separate plan and quota cannot be shared amongst sites.
Note - each website will also have a different script.