There's a solution for this dilemma. 
What is the solution?Well you cant really use btc as a virtual currency because it is a cash equivalent. You can sell tokens for btc though. As long as you cant cash the tokens out for any cash equivalents immediately you wont face any repercussions. Once you have the tokens you can use them like any other virtual currency. This is the same reason you cant just use cash and claim it is a virtual currency. Tokens that you can earn however could be cashed out once your users got to an agreed amount.
Bitcoin needs its own virtual currency fork to be used as an in game system and not break the terms of service of zynga,super rewards and other virtual currency products.
If btc had been setup as virtual currency from the beginning it would be different,so now it has to be done differently.
Since when is bitcoin a cash equivalent?
It could be considered as such for some purposes because it is a store of value. In strict financial terms, it is not one. Regardless, it doesn't (In my understanding) invalidate its use as game "currency."