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The Kepler license is a file (usergrouppicker-pro.lic) which must be placed in the <JIRA_HOME>/kepler folder. You can either generate and download a free evaluation license by registering on our site and accessing the Licenses section, or you can purchase the plugin by following these instructions.
You can view details for your kepler license by accessing the Kepler Licenses page from Kepler General Parameters -> Licensing menu:
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