In the beginning, there was Red Hat Linux[1]. It was sold in boxes at stores such as CompUSA (remember?) but was also available for free download from Red Hat.
Then, Red Hat decided they could make more money by spinning off Red Hat Linux into a separate enterprise-only product called Red Hat Enterprise Linux (RHEL), which they declined to make available for free in a ready-to-install binary form. Fedora[2] was also spun off at this time, as the free successor to Red Hat Linux that was supposed to be only suitable for home users. Fedora development was/is sponsored by Red Hat but they did not offer end-user support, in contrast to RHEL.
Meanwhile, there was demand for a free version of RHEL. Since it was built with GPL software, Red Hat was obligated to make it available in source form, but their trademark policy prohibited anyone else from using the Red Hat name. Therefore, a group of volunteers took RHEL, removed Red Hat trademarks, and called it CentOS. To avoid confusion, CentOS explained the origins of the distribution on their web site. For their efforts, they were threatened by Red Hat's legal department and forced to remove all mentions of Red Hat and even links to Red Hat's web site from the CentOS web site. CentOS complied and began referring to its Red Hat derivations using the euphemism PNAELV[3].
Now, Red Hat has again decided they would benefit from being more directly involved in providing an open-source, freely-available enterprise Linux distribution. We've come full circle.
(Flippant depiction aside, I intend no antagonism, but merely find the history of these projects interesting.)
Then, Red Hat decided they could make more money by spinning off Red Hat Linux into a separate enterprise-only product called Red Hat Enterprise Linux (RHEL), which they declined to make available for free in a ready-to-install binary form. Fedora[2] was also spun off at this time, as the free successor to Red Hat Linux that was supposed to be only suitable for home users. Fedora development was/is sponsored by Red Hat but they did not offer end-user support, in contrast to RHEL.
Meanwhile, there was demand for a free version of RHEL. Since it was built with GPL software, Red Hat was obligated to make it available in source form, but their trademark policy prohibited anyone else from using the Red Hat name. Therefore, a group of volunteers took RHEL, removed Red Hat trademarks, and called it CentOS. To avoid confusion, CentOS explained the origins of the distribution on their web site. For their efforts, they were threatened by Red Hat's legal department and forced to remove all mentions of Red Hat and even links to Red Hat's web site from the CentOS web site. CentOS complied and began referring to its Red Hat derivations using the euphemism PNAELV[3].
Now, Red Hat has again decided they would benefit from being more directly involved in providing an open-source, freely-available enterprise Linux distribution. We've come full circle.
(Flippant depiction aside, I intend no antagonism, but merely find the history of these projects interesting.)
[1]: https://en.wikipedia.org/wiki/Red_Hat_Linux [2]: https://fedoraproject.org/en/about-fedora [3]: http://www.pnaelv.net