CentOS, a white-box twin of RHEL
Since version 3.0, CentOS (Community Enterprise Operating System) has been a certifiable white-box twin of Redhat Enterprise Linux (RHEL). CentOS 3.* mirrored the RHEL ES 3.* series, while CentOS 3.* mirrors the RHEL AS 4.* series.
CentOS core developers vowed to keep CentOS as close to RHEL as possible, and to manage any deviation with extreme caution. In fact, it compiles off the same source rpm bundle that RHEL compiles from, minus the arts and logos belong to Redhat Inc. Efforts is made to mimize the changes in CentOS. For those truly necessary, they get documented and fed upstream.
As it stands now, CentOS seems to be the apparent winner in SMB space, for its cost: $0 + optional donation recommended at $100/node/year. Clients I consults usually postpone the honorable donation forever, or till a better time in the future.
