Or for newer versions:

within 90 days of expiration to get access to newer versions. Troubleshooting Common License Errors "Search is not available"

Editing the registry is risky. Back up your registry first.

: If you have 15 or fewer users and do not need advanced features like Active Directory SSO or VDFS replication, you can switch to the free Community license . Go to Action | All Tasks | Update License | More actions | Switch to Community license .