There are already several clones of Red Hat Enterprise Linux (RHEL), the most popular being CentOS . But all are small, open-source projects that lack the backing of a multibillion-dollar software company with a reputation of being aggressive.

In a posted the day after Ellison announced Oracle's incursion into Red Hat's core support business last week, Red Hat was adamant that Oracle will deviate strongly from Red Hat and customers will suffer.

"Simply put, this derivative will not be Red Hat Enterprise Linux and customers will not have the assurance of compatibility with the Red Hat Enterprise Linux hardware and application ecosystem," the statement said. Hardware and software certified for RHEL will become "invalidated" with Oracle's flavor, according to Red Hat, and Oracle support customers will experience a delay in getting the latest updates from Red Hat, especially security patches, the company said.

"In the case where the update corrects critical security flaws, Oracle customers may be exposed to additional risk," Red Hat said.

Oracle officials did not return a request for comment.