The biggest distributor of the Linux computer system has waded into a row over claims that its creators have broken copyright by suing the company making the accusations.
Red Hat, which sells a widely-used version of the open-source operating system, has started a fighting fund with a $1m donation intended to cover the costs of anyone choosing to hit back at SCO, the company which claims it owns part of Linux.
SCO has been threatening to sue Linux users large and small, saying that code it owns - bought from computer software house Novell - has been illegally recycled into Linux by some of the thousands of programmers who built the free-to-copy system.
Now, though, Red Hat is countersuing, accusing SCO of "unfair and deceptive actions".
Suit and countersuit
The row over Linux started with a billion-dollar suit levelled at computer giant IBM by SCO, which said IBM's distribution of Linux breached its copyright.
It followed that up with letters to 1,500 users of Linux, warning them that they, too, could be liable to be sued.
It has now offered to sell licences to end-users and software houses which it says will protect them from the threat.
But Red Hat - not to mention many in the Linux community - believe the threats to be little more than shadow boxing, an attempt to leverage intellectual property by a company which now is equipped to do little else.
In a memo to sales staff, IBM's management said SCO "is asking customers to pay money based on puire unsubstantiated threats, without offering any facts".
A survey by research firm Evans Data of some 400 software developers found 70% felt SCO's attempt was doomed to fail.
SCO shares fell almost 20% after Red Hat's announcement, but later recovered to end the day down 8.8%. Red Hat shares ended down 3.8%.