Learned something new (although I slightly remember reading this before)
According the DLNA website the WDTV Live supports both DMP (player = what PMS supports) and DMR (renderer = can push content to it). But as chocolateboy
said, PMS has no support for it currently, although I don't see why it couldn't be possible in the future, provided there's somebody that actually wants to implement it and handle the massive scope change.
's mlx plugin idea sounds like a good place to start.