You can go to this link: https://bitcointalk.org/index.php?board=71.0
It is indeed great to see their mirror links on their landing page. This will assist players to use those links in case they are encountering some issues. Also, they will know right away that those links are legit.
However, one thing I that players should be aware of is their KYC protocol. It seems that it is mandatory before you can withdraw on their site, as they have their license in place already. You can also check their KYC section here - https://gamegram.com/faq/?q=kyc.
So before you avail their deposit bonus and their wager free promo for cashback, better check out if your kyc is already verified successfully.