I'm planning to add a DLNA compatible DVD/Blue-ray player to my home theater setup. I also have my Windows Home Server with a lot of videos and photos.
Can a DLNA DVD player connect to my Windows Home Server and stream videos without any additional software on the WHS?
DLNA (DLNA on Wikipedia) is a big honking beast of a standard; certifying a device as "DLNA compatible" doesn't really say anything about what it will work with. The specification categorizes devices into several categories:
Wikipedia notes that "any PC with a network interface can become a DLNA device by installing DLNA software". And given the right software, the PC could act in almost any of the roles listed above.
However, whether the DVD/BluRay player can stream videos from a DMS depends on what DLNA roles the player fulfills. It needs to act as a DMP or DMR to play content from a DMS.