I'm a great fan of no one's streaming music service at this point, and Beats Music is no different in that regard -- too limited a catalog to be single-source, no lossless streaming option for audiophiles, no universal family subscription option (AT&T-only), and in Beats' case, no desktop client, meaning you'll have to grapple with a quirky web interface (quirky being a universal bête noire) instead.
But Beats' announcement today on its developer page that it's moving to an open API is a clear step in the right direction. It's not a step past its main competitors, meaning services like Rdio and Spotify, both of whom already offer open APIs, but it's the step Beats probably needed to take to get its service onto a broader array of platforms.
Beats already had a deal in place with Sonos, but this takes that sort of deal out of the realm of proprietary and into one where any developer can plug into Beats' ecosystem. Imagine the auto industry hopping on board, or TV manufacturers, or any device capable of accommodating Beats' requirements.
In short, developers will have to register their application, get an access token, plug into the API, then ensure access tokens are properly refreshed. Developers that want to test out Beats' API can use something Beats calls Playground, "a convenient online tool that lets you run our APIs with just a few mouse clicks."
I don't have Beats' subscriber base numbers (no one does), so I'm skeptical about casual claims that the service is wildly popular, but assuming those claims aren't off the mark, it'd lend credence to Beats' assumption that the sort of casual listener Beats is targeting wants a mix of control and curated content instead of one or the other. That's the tune Beats is humming, and if enough developers are enticed by the prospect of plugging into its ecosystem, it's a tune you'll probably see Beats' competitors eventually take up, too.