One CPU license is required for each CPU of the server(s) running your application/system which embeds edit-on Pro. It does not matter how edit-on Pro is technically separated from your application/system. Regardless of where or how edit-on Pro is loaded, all CPUs that serve  the application/system which embeds edit-on Pro have to be licensed. For detailed information please review the "CPU definition" within the edit-on Pro Software License Agreement.