Oracle's entrance in cloning RHEL is pure profit plain and simple. Their value add is "tailored" support for Oracle platform and products. They do support bug fixes just as Centos does. I use both Centos and OEL. OEL contributes clustering file-system technology that is incorporated in the Kernel. All patches from OEL are GPL. Echoing above, the base OS is still pure RHEL. Other packages are purely addons such as YasT. Remember they are charging for the Support, the distro is a free DL