Brian Stevens, the chief technical officer of the company, who offered this explanation towards the end of an eight-paragraph blog entry attempting to explain the sudden change, did not respond directly to questions sent to the company by iTWire.
As reported in these columns, the change was first publicised in an interview given by Maximilian Attems, a member of the Debian kernel team. It received further publicity on the Linux Weekly News website.
A number of other publications have since reported the issue.
Stevens spoke to the British technology website, The Register, and named the two competitors for whom Red Hat wanted to make life difficult - Oracle and Novell.
However, Stevens said nothing about the fact that Red Hat could well be violating the GNU General Public Licence under which the Linux kernel is released.
The GPL specifies that additional restrictions cannot be placed on redistribution of GPL-ed sources. Red Hat's policy now is to cancel the support options for any of its subscribers who redistributes the source of its kernel.
In his blog entry, Stevens said Red Hat's competitors had now changed their tactics, and, instead of offering their own GNU/Linux contributions as alternatives, were trying to lure away its customers by offering to support its own enterprise distribution, Red Hat Enterprise Linux.
"Frankly, our response is to compete," Stevens wrote. "Essential knowledge that our customers have relied on to support their RHEL environments will increasingly only be available under subscription.
"The itemization (sic) of kernel patches that correlate with articles in our knowledge base is no longer available to our competitors, but rather only to our customers who have recognized (sic) the value of RHEL and have thus indirectly funded Red Hat's contributions to open source that will advance their business now and in the future."
Red Hat's tactic does not prevent either Oracle or Novell taking out a single subscription each to RHEL and profiting from all the work done by Red Hat.