Apple has taken its liberty and tweaked the firmware code in the iPod that was previously reverse engineered by Real Networks to allow songs from Real to be played on the iPod.
Only discovered very recently was that Apple has changed the firmware code on the iPod to not allow RealŐs Helix DRM system. There is some head scratching however over when Apple actually changed the firmware code. There was an update in October that seems like the one as the firmware update on November 15 was only for two models of the iPod. Since it has only now, a month and a half later, that the news has been widely publicized it seems that RealŐs Freedom campaign was not as overly successful to iPod users as Real had hoped.
For the full story:
The Register - Apple iPod out of tune with Real's Harmony