Licensing is based on a per production Web Front End (WFE) server. You need to obtain a valid Server License for each production WFE server in your SharePoint farm.
There is no restriction on the number of web applications, the number of site collections, the number of developers/designers working with the web part designer and no restriction on the number of viewers.
Subscription gives you access to all minor and major version releases within one year after purchase, priority support (plus 5 additional support tickets with your purchase). You may renew your Subscription after the first year to continue to receive updates and priority support.
