I was planning on writing a simple html5 card game with online multiplayer, would this combined with some basic sessioning logic help with server-client interactions for the gameloop ?
Sure. You first need to figure out how to represent your game data in terms of object/collection resources. Then LiveResource makes it easy for clients to receive updates to those resources in realtime.
would this work with CHAIN? a bitcoin api
If Chain implemented the LiveResource protocol, then the JS library could work with it, sure. Their Bitcoin address objects seem to support ETags properly so the groundwork is done.