As far as I know,domain for life is usually promised with other preconditions such as using their web hosting or other service.If you stop using the corresponding service,it will no longer be free.Domain name has its cost,so none of the providers will charge you free without any condition.If you only want to buy a single domain name,you'd better buy it from some special domain registrars such as godaddy,name and etc...
we'll they may not be a scam. not having access to your domain so you can switch hosts if you run into trouble is a big problem. As for reviews they arnt that favourable for justhost. there system is also buggy. theres a way to signup for a year for free with them+ domain. (WHICH) i assume is a mistake.