You are right I think, at the end of the day they could just handle the packet sending/receiving themselves to support distribution outside of Steam. But if the

You are right I think, at the end of the day they could just handle the packet sending/receiving themselves to support distribution outside of Steam. But if there is a barrier in the SteamWorks API to prevent that somehow (which is unlikely I guess though my memory of the API is hazy), then Steam would be to blame. Assuming there isn't a barrier, then really it is Activision's fault for not integrating the network code properly so Steam and non-Steam players can play together. in either case, I fail to see how this is the Windows Store's fault.