Configuration Manager for Jira needs to be licensed on all instances where it's used.
A commercial license is needed on all production Jira servers for doing production work. Every commercial license comes with an unlimited number of developer licenses that can be used on non-production Jira instances corresponding to the one where the commercial license is installed. E.g. in a Test-Staging-Production scenario a commercial CMJ license is needed only on the Production Jira.
For a migration a commercial license is needed only for the target production Jira server. For the source production Jira server, you can also use commercial or trial licenses, or you can reach out at our Support Portal, and we can provide you with a free license.
You can use a trial license for evaluation purposes only.