There are 3 license types for Harepoint Workflow Manager Extensions:

• Trial License. Provided for a 30-day period to use the product in the organization’s environment without any limitations of product functionality.
• Free License. This license allows using the product with the Free Set of Activities without limitation of number of servers or usage time. After expiration of the Trial License, the product will continue to operate under the Free License by default. The set of available activities will be limited to the Free Set. Execution of workflows created by using other activities will be terminated with errors.
• Full License. This license is purchased for a given number of SharePoint Servers and allows using the product in the organization’s environment without limitation on usage time or on available activities.

Subscription
The Full License comes with a 1 year subscription which includes technical support and all version updates released within the subscription period.
The subscription can be renewed on an annual basis providing you with an additional 1 year of technical support and product updates.
If you do not renew your subscription you will still be able to use the product however you will not be eligible for technical support or product updates.