I did know that Apple Fairplay can play on iOS, tvOS, macos in safari by apple documents. https://developer.apple.com/streaming/fps/
But I think that some macos APIs looks like it can play fairplay in macos app. In macos release note, for example, they said
Added FairPlay streaming key management. Improved the functionality of AVContentKeySession. Use AVContentKeySession to initiate content key requests independent of playback or downloading of media assets. Objects conforming to the AVContentKeyRecipient protocol, such as AVURLAsset, can be added as a recipient to AVContentKeySession to obtain access to existing content keys and initiate new content key requests.
Can I use Apple Fairplay in macos app?
Yes, FairPlay Streaming is available in macos.