Can anyone please clarify the type of open source license of Prefect server? Is there any licensing impact using in production?

I'd say that while it is not -- strictly speaking by OSI definitions -- an open source licence, it is a source-available licence on the open source end of the spectrum, and should not have "any licensing impact using in production" as long as your production system isn't competing with Prefect Cloud to provide an external service. Having said that, I am not a lawyer and this is not legal advice.

From a quick inspection of the GitHubs, Prefect Core is licensed under Apache 2.0: https://github.com/PrefectHQ/prefect/blob/master/LICENSE …and Prefect Server and UI are licensed under the "Prefect Community License": https://github.com/PrefectHQ/server/blob/master/LICENSE https://github.com/PrefectHQ/ui/blob/master/LICENSE