Although Microsoft suported flip4mac project that allows Windows Media audio and video files to play on a Mac, it has never supported playing DRM-protected Windows Media content on anything besides Windows. Users of BBC iPlayer were limited to Windows.

Luckily current version of MPlayer does support DRM protected Windows Media WMV files. So MPlayer allows you to watch DRM-protected Windows Media WMV videos from BBC iPlayer in Linux / Unix / MacOSX !

Please note that this method doesn't allows you to watch DRM-protected streaming videos and watch videos with one-time play licenses.

See the following thread for more:
How to watch/listen DRM protected Windows Media .WMV/.WMA files in Linux/Unix/MacOSX