I suspect they are merely waiting how this whole Bitcoin Cash thing plays out
It's already played out. They clearly gave it a LOT of thought by suspending withdraws for two days before the fork. This is an amount of time that was longer than literally every other gambling site or exchange. The fork happened two weeks ago. Since then, nearly every other gambling site and exchange has given the bitcoin cash to the people that held the funds at the time of the fork. There is no reason for Nitrogen to not do the same to it's players.
...although they have over 1.3 million reasons why they might not.
Maybe they are working on implementing the possibility of betting with your Bitcoin Cash balance. This could
for sure take some time. It would be in their interest to let users gamble with their BCC/BCH, because otherwise
everyone would simply withdraw it.
I wouldn´t be so fast in condemning Nitrogen for keeping the Bitcoin Cash. Let´s revisit this in a month

You are aware that major businesses like Coinbase have still not done the "right thing" according to you as well?
In a blogpost on Thursday, Coinbase Director of Communications David Farmer said the exchange intends to support the new Bitcoin Cash currency by January 1, 2018 "assuming no additional risks emerge during that time."