Here: Get All Features
is this, “If you decide to purchase the upgrade, you permanently unlock all current premium features across all of your Macs. Each of them is described in detail below.”
Note, not just Macs, right? iOS too?
In principle yes, if you buy the premium features either from within Agenda for Mac, or you buy the corresponding mac+iOS option from within Agenda for iOS. If you buy the iOS only option from within Agenda for iOS they unlock across all your iOS devices (only).
I’ve changed the text to mention “devices” instead of “macs”, thanks for pointing this out.