Last.fm is banning all unofficial third-party apps that allow users to stream its content, including those that stream to mobile phones, the CBS-owned online music site posted yesterday in its discussion forum. It’s planning on releasing its own official streaming API, and developers who use it must sign up for an API account. The new API also comes with two specific limitations:

—Only subscribers will be allowed to stream using third party applications, unless the developer of the app negotiates a separate deal with the Last.fm. The music site said they needed to do this in order to get the money to cover royalties.

—Apps that stream to mobiles will be cut off. Last.fm blamed its licensing agreements as not allowing this. Again, developers were told to contact them to see if “an exception” could be worked out.

The news comes a day after the music site said it would begin at the end of March to charge €3 ($4) a month for “Last.fm Radio” – what it defines as personalized, back-to-back full-track streams everywhere except the UK, U.S. and Germany. As GigaOm notes, put the two new moves together and its clear Last.fm is trying to figure out a way to move beyond a post-advertising business model, and fast, especially with CBS (NYSE: CBS) facing the same “dire straits” as most media companies.

• Last.fm Puts Pay Wall Around Streams; Except In US, UK, Germany