[mdmarra]

There are some misconceptions here. RHEL does not cost a cent. Support for RHEL, which includes security fixes through the package manager costs money. Security fixes and other patches and updates are still released as source by RHEL, as required by the GPL.

If you really wanted, you could run RHEL with no subscription and compile your own updates from the source that they release. In practice, this is next to impossible to maintain as an individual, but it is exactly what CentOS, Scientific Linux, and other related EL distributions do. They remove the RHEL trademarked logos, compile the code released by RHEL, and make it available through a generic yum repository that doesn't require a RHEL subscription.

So, in short, RHEL doesn't cost money, support and packaged patches do. CentOS gives you binary and version compatibility of RHEL without the cost.