The Rockbox project further extended this codec to be suitable for embedded cores, allowing playback on portable MP3 players and cell phones running open source software. RealNetworks has announced plans to support playback of DRM-free WMA files in RealPlayer for Linux.[56] On the Macintosh platform, Microsoft released a PowerPC version of Windows Media Player for Mac OS X in 2003,[57] but further development of the software has ceased. Microsoft currently endorses the third-party Flip4Mac WMA, a QuickTime component that allows Macintosh users to play WMA files in any player that uses the QuickTime framework.[58] Flip4Mac, however, does not currently support the Windows Media Audio Voice codec.[59]