Yes, he can even use the free RHEL Dev licenses, he just doesnt want to bother with any kind of licensing system.
Alas, this was before Red Hat bought CentOS :(.
He didn't do free work for their platform. He did work using their platform which he made freely available to further his own situation. I don't say that in a judgemental way. There is nothing wrong with that, but let's not misrepresent it.