Hi, does anyone know whether I can integrate Prefect on-prem, as part of my product, without paying for a subscription?

There are two parts to Prefect. The core and the backend. The core is the interface you code in, the backend are the set of services that help with the orchestration. The backend you use can either be Prefect Cloud or Prefect Server (for Prefect 1). Cloud is our hosted version, Server if you hosting it. Server is fully open source and you can find it here

Thanks @Kevin Kho! And the server doesn’t cost money?

No it’s free