How can frogs tolerate freezing while humans cannot?
Generally frogs are cold blooded animals (more specifically ectothermic or poikilothermic) . Wood frogs can maintain their body temperature by production of cryoprotectants which a human body cannot produce from normal metabolic processes. Such molecules depress the freezing point of tissue and avoid ice formation. Here is a scientific report on the physiology of wood frogs and what helps them survive at freezing temperatures. There are also other mechanisms which cold blooded animals use to survive such conditions. 

Now for the human part. Humans are warm blooded (more specifically endothermic). We always try to maintain their body temperature (our normal body temperature is $37^{o}$). That is why we cannot tolerate freezing temperatures, because our physiology does not have a means to avoid cell damage at that temperature. The company which you mentioned uses vitrification methods which uses various artificial cryoprotectants (which wood frog makes naturally). 

There is research going on in this direction already. Researchers are using extremophiles and their metabolic products in cosmetics and medicine (like this, this and this).