Uh
you guys are getting way ahead of yourselves. It not habitable for us, We'd only be able to live right in the center between the shadow section and the side facing towards the light. G581g doesn't have an axis that it rotates around, so it's temperature is constant. We don't know if it has an atmosphere or water.
The only reason we're so excited is because it it in the predicted Goldilocks zone of Gliese.
SECOND, the theory of how life started here is that amino acids formed a perfect sequence to create DNA, therefore creating the first "life." The chances of it actually occurring in the life of our universe (which could end) is abyssmal and the fact that they're giving it 100% chances is ridculous. Earth gaining life was probably one of the least likely things possible to happen.
Plus, with the formation of archaebacteria, we should also take into account that species can learn to live in extreme conditions.
Even if life did form, we assume that living things need water and oxygen, but thats only because we're aware of our kinds of life, not other possible kinds of life. There could be Nitrogen breathing... Helium breathing... methane breathing, even, species of life.
EDIT: plus, Gliese is 20 lightyears away, so the planets and the start that we're seeing is twenty years into the past.