In a bit old, but interesting article, High Fidelity Review discusses the DVD-AR, recordable DVD-Audio, specifications they received from Bike H. Suzuki, the chairman of DVD Forum WG-4.

With DVD-AR users can record, edit, and replay audio content on writable discs. The format can be used for various purposes thanks to a wide variety of lossless and lossy compression schemes. There are two lossless formats (linear PCM and packed PCM) and six lossy formats (Dolby Digital, DTS, MPEG-1/2 Layer II, ATRAC-3, MP3PRO, and MPEG-2 AAC). There's no need to have a lossless PCM track on a disc, so it is possible to store hours and hours of multichannel audio on a single disc. Users can also store still pictures and text on DVD-AR.

4C who developed the content protection scheme used on DVD-Audio discs is developing a compatible system for DVD-AR. Unlike DVD-Video, DVD-Audio copy protection is, as far as I know, yet to be cracked.

The DVD-AR -format is a welcome addition to the DVD standards family. The news article doesn't discuss the DVD-AR media, but I think it's safe to assume it will not be compatible with DVD+R(W) or DVD-R(W). The final standard should be available this month.

Source:
High Fidelity Review