That's crap. Total crap.
What they say is
We will review your website in a week and if your website meets our minimum requirement of 100 unique visitors per day then we will give you your domain for FREE.
Great.
So you get the name, you advertise you site everywhere, hoping it will get the 100 unique visitors a day, you print the address on your cards, give them to friends, use it for your email, and then
- you don't make the 100
- you make the 100 but after 6 months you miss them
And then? How much will you have to pay to keep the name?
Because by then you spent so much time on it that you will have to keep it.
And what kind of webhosting do they add to it, if any?
There's nothing like a free lunch, and a domain name - just the name, no hosting - you get for next to nothing nowadays anyway.
And if you buy the name then it will be yours forever and not subject to undocumented and/or dubious business plans.
My tip: Forget about it.