I don't get it. How is it Thinkpad X-something, and yet "made by a group of enthusiasts, not a big company"? Is it an illegal rip-off? Is it Lenovo lending thei

I don't get it. How is it Thinkpad X-something, and yet "made by a group of enthusiasts, not a big company"? Is it an illegal rip-off? Is it Lenovo lending their name to someone else? What is this 51NB exactly?