My understanding is that they can't sell
Redken because Redken only sells to salons. I think Redken gives them a bunch of bottles for distribution for free to get the word out (especially if someone likes it and it spurs a few happy posts). Some freebies have been amazing for me. Others have been so-so to yucky.
Ironically, the big-name brands (Matrix Curl Life comes to mind) have been lousy so that it seemed their freebies were intended to get the word out but were such bad products that it wasn't advantageous since so many nc.com-ers hated those products. But the smaller companies (Jessicurl, Curl Junkie, AG) who have provided samples have gotten to introduce curlies to their products and that technique has been advantageous to them.