从维基:
Red Hat Enterprise Linux is available only through a paid subscription service
that provides access to software updates and varying levels of technical support.
The product is largely composed of software packages distributed under either an open
source or a free software license and the source code for these packages is made
public by Red Hat.
CentOS developers use Red Hat's source code to create a final product very
similar to Red Hat Enterprise Linux. Red Hat's branding and logos are changed because
Red Hat does not allow them to be redistributed.[5]
CentOS is available free of charge. Technical support is primarily provided by
the community via official mailing lists, web forums, and chat rooms. The project
is not affiliated with Red Hat thus receives no financial or logistical support
from the company; instead, the CentOS Project relies on donations from users and
organizational sponsors.