Can I Use Shared Genesis/Thesis Framework For WordPress?

Anyone who is using WordPress or is a developer for it must be well acquainted with these two names as they prove to become the two best frameworks ever. I got to know that both of these are licensed under GNU-GPL which allows sharing/redistribution of the software by peers. So like if I manage to get the framework(Genesis or Thesis) from a friend of mine who has actually purchased it then would I be able to use it LEGALLY on my blog? or is it illegal ? Please explain this.