This is just 1:1 copy paste of original GrinGoldMiner and the only change is that they changed the name (even that they screwed up, still reports as GGM in pools) and they take the fee for themselves. With that they are in violation of the fair mining licence.
They also lie about speed improvement, their binary blob of the solver has same sha256 hash as the GGM original they took it from.
They are just scammers. Be careful, they may also add some "bonus", would not surprise me.
Just use the original GrinGoldMiner (find it in GitHub), dont fall for these cheap clones.
urza (one of authors of GGM)