Behave Pro is licensed and sold via the Atlassian Marketplace, and implements the licensing rules from Atlassian.
For Behave Pro you are required to purchase the license tier that matches the number of users you have licensed for your host application. For example, if you have a 25-user JIRA license, purchase Behave Pro at the 25-user tier. Behave Pro will only function if its license matches or exceeds the tier of JIRA – even if only some of your licensed users need to use the add-on.
With JIRA it is possible to have different numbers of license users for each JIRA application (JIRA Core, JIRA Software, JIRA ServiceDesk). You must purchase the add-on license that matches the highest JIRA application tier. For example, if you have a 500-User JIRA Core license, and a 25-User JIRA Software license, you must purchase the 500-User level.
This article is based on the Atlassian Marketplace FAQ