The clientseed is generated randomly in the browser - not on the server.
I think it's currently being generated by server. When the user makes a bet, it does a POST request to:
/ep/ajax/?func=placeBetDice
which returns a field:
csNext
which is then used as the next client seed. Although I'm really not sure why they're not using the gist I provided in the thread (generating client seeds on the server actually seems like more work, tbh). But I'm assuming it's on the TODO list in the next update.