is working on releasing a set of software tools that will let third-party developers create applications using its music streaming service.

As a first step in that process, the company is banning any applications currently using the service to stream music without expressed permission.

The official licensing program will carry restrictions: only paying subscribers will be able to stream music through those third-party applications, and it will not support streaming to mobile phones unless a more direct deal is negotiated beyond the software licensing.

Both the restrictions and the decision to ban unofficial applications stem from music licensing agreements in one way or another. The company says the deals in place with music labels do not cover mobile streaming, for instance. But more broadly, the move is another attempt to generate revenues in the face of its music royalty payments.

Earlier this week, said it would begin charging a monthly subscription fee of about $4 a month to users in all countries outside of the U.S., U.K, and Germany, ending the free ad-supported service in those areas because it was unable to sell enough advertising to cover its costs there. says the change in the development tool availability should go into affect by the end of next week.