Datacenter - Unlimited Website License 
This premium license provides access to all site building features and also removes all internal 'Rate Limits'. It also provides multiple site hosting and a complete billing and payment system for managing hosted sites for SaaS or Cloud delivery. It is available either for outright purchase, or on a 'pay-as-you-go' monthly basis.
 

Who uses an Datacenter - Unlimited Website License?

Website Development Companies
The Datacenter license provides a full hosting and billing system so that website development companies can host their customers websites on their own server and then bill them monthly. The system manages everything from hosting to metering to reminders and credit control. This license enables you to host an unlimited number of websites and have an income stream from each one - all managed automatically.

Corporate
If you have multiple domains and independent websites and microsites for different products or services, then the Unlimited license is your best choice. In addition to hosting an unlimited number of websites the internal accounting system can be used for 'profit center analysis'.

Education
An Unlimited license allows a school or college to host an unlimited number of 'class' or project based websites, without the page delay found in the Free License - and gives access to Support services.

Web Development licenses are Free

In most situations a web development company does not need a Datacenter license simply to develop a website or web application for a customer. New websites are Developed using the Free license, and it's the end-user who purchases the Premium license either individually or as part of the package from the Developer.
Read more in the Explainer explained...