Being able to play AAC, Zune Software can import music from the iTunes but only non-DRM tracks. This was expected but of course a confirmation is always welcome. Zune DRM and iTunes DRM are incompatible so you cannot take a track you bought on the Zune Marketplace and play it on iTunes or iPod. In a similar way you cannot take a track you bought on on iTunes and play it on the Zune Software or the Zune device.

And what is the meaning of this?

You can take the (non-DRM) songs you have imported from other sources into iTunes and import them (complete with ratings) to the Zune software and the Zune device. 

Source: GizModo

Link: View Zune Codecs and Download the Software.