WMDRM (Windows Media DRM) is a technology from Microsoft to securely protect and deliver media contents.
WMDRM is available in PC, portable device and network device. It includes mobile phone as well. Mobile phone can be categorized as portable device if it plays the contents offline or as network device if the content is streamed to the device.
There are some S60 devices that support WMDRM already, such as Nokia N91 and N76. They can only play the contents offline. Note that not all Nokia devices that are part of Xpress solution support WMDRM.
Microsoft initiated a standard, called PlaysForSure that allow compatibility between various devices and content providers. A device with PlaysForSure logo shall be able to play contents distributed by any providers with PlaysForSure logo.
Third parties can download Windows Media Rights Manager SDK to deliver contents in WMDRM. It is shipped with the tools for protecting the contents as well comprehensive documentation.
There is an SDK from Microsoft, called Windows Media Format SDK, that allows third party to build player application for WMDRM. Unfortunately, the SDK is mostly targeted for Windows platform.
As of the writing of this article, there is no SDK for S60 yet. Although there are some Nokia devices that support WMDRM already, but the API is not publicly available.