Apple [via PRNewswire]:

We are stunned that RealNetworks has adopted the tactics and ethics of a hacker to break into the iPod(R), and we are investigating the implications of their actions under the DMCA and other laws. We strongly caution Real and their customers that when we update our iPod software from time to time it is highly likely that Real's Harmony technology will cease to work with current and future iPods.

RealNetworks:

Harmony follows in a well-established tradition of fully legal, independently developed paths to achieve compatibility. There is ample and clear precedent for this activity, for instance the first IBM compatible PCs from Compaq. Harmony creates a way to lock content from Real's music store in a way that is compatible with the iPod, Windows Media DRM devices, and Helix DRM devices. Harmony technology does not remove or disable any DRM system. Apple has suggested that new laws such as the Digital Millennium Copyright Act [DMCA] are relevant to this dispute. In fact, the DMCA is not designed to prevent the creation of new methods of locking content, and explicitly allows the creation of interoperable software.

We remain fully committed to Harmony and to giving millions of consumers who own portable music devices, including the Apple iPod, choice and compatibility.