I do realize thatās not all up to you and likely even comes with a cost. And will take time. Iām sure you are and have explored more partnerships in addition to Tidal but even though they have a large library of titles, not many I would listen to. I am one of many but mostly listen to classical and have been subscriber many years to Amazon Music, now getting HD for free. Until then I will need to purchase cdās and import them into Audirvana Studio to get higher quality which is of course doable. For those of us dedicated classically, Idagio and Primephonic are high quality and have much larger classical libraries but integrating Amazon would benefit many more of your own customers while having huge number of titles of any musical genre.
Actually you should ask Apple or Amazon. For what I have read on different forums both Apple and Amazon are not likely to allow other programs to integrate Amazon HD or Apple Music in the near future (or at all).
EDIT @VoyagerDude just gave a link to Apple, where Apple offers a Developer Kit to integrate Apple Music into oneās program. Did not see that before. So forget what I said about Apple.
Not sure if you saw this Apple Developer Documentation
Oh wow. I did not see that. Canāt believe my eyes 
.
I will edit my previous post. Thanks for pointing that out.
Ah, that means
A) It will only be available for Apple hardware
B) Audirvana can probably not use itās own built in sound engine / or bypass the sound engine of the Apple Music player.
Basically this means that Apple Music in Audirvana will not have the same Sound Quality as the rest of Audirvana. Also it means that Audirvana for Windows can not incorporate it.
But, as you said, the info is still very spotty, so we can only wait and seeā¦
Yup, thatās what I am able to deduct so far from the docs as well.
MusicKit uses the Apple Music API web service under the hood
https://developer.apple.com/documentation/applemusicapi/
But the problem is that I cannot find a songās stream url in the API docs.