CentOS is a commercial distribution of Linux based on the RHEL source code; Since RedHat develops its products through open source software, it tries to generalize its source code, although CentOs releases versions based on the RHEL code and similar to it. CentOS versions rebuild RedHat versions. But there are also differences between them.
CentOS is not RedHat certified because it is based on source code only. CentOS, for the production of binary packages, Uses RedHat public resource packages which are freely available to the public; In fact, CentOS is a free option for business and enterprise users. RedHat has also supported CentOS since 2014 by forming a board of directors between CentOS developers and RedHat to assist open source developers in developing CentOS.