Highend Theme Usage

Hey!
I bought the Highend theme and am using it for FST Logistics. I previewed it for them last week and they were stunned at what I configured for them. Today, FST Logistics has a web-site that in 70% dedicated to drivers. We are going to move that web-site to drivers.fstlogistics.com and install the new site on the primary domain. Can we still use Highend on drivers.fstlogistics.com or is that a separate license purchase? Not clear on how the license works with subdomains.

Thanks for your help!