Red Hat has hit back at SCO's claims that its code is included in the Linux kernel, launching a 'put up or shut up' lawsuit which aims to force the Unix vendor to either prove its case or withdraw its accusations.

It has attacked SCO's attempts of "extortion from unfounded and baseless claims" and set up a $1m fighting fund to support Linux developers who fall foul of SCO's legal actions.

"We are going on the offensive," said Matthew Szulik (pictured), chairman and chief executive of Red Hat, as his company detailed the seven-point lawsuit against SCO.

"Red Hat has a responsibility to ensure that the legal rights of users are protected," he added.

The company explained that the impact of SCO's actions on the open source community, Linux users and Red Hat itself have forced it to act.

It also believes that SCO's actions have given it no alternative but to turn to the courts.

"Had we been able to inspect the code we would not have to do this," stated Szulik.

The lawsuit seeks a declaration that Red Hat is not violating SCO intellectual property or misappropriating SCO trade secrets, and an injunction that would bar SCO from making untrue claims which could harm the Linux business.

Any action could take up to 18 months to be completed, according to Red Hat, but the company believes that reaching a decisive conclusion is key.

"If there is intellectual property infringing code it can be reversed quickly, but all we have now is hearsay and innuendo," said Szulik.

The $1m defence fund, dubbed Open Source Now, is for companies that may have to face SCO in court to defend its infringement claims.

The money will cover legal expenses associated with infringement claims against companies developing software under the GPL licence.

"We are putting our money where our mouth is," said Szulik.

Red Hat maintained that it is especially concerned about the impact of SCO's claims on many of its customers.

SCO has already sent letters to 1,500 large companies using Linux warning them that they may be held liable for using any version of Linux that contains SCO code.

"SCO has brought our customers into this process. It is threatening them with extortion from unfounded and baseless claims and we had to step forward on their behalf to establish the truth," said Szulik.

For its part, SCO has reiterated that its claims are true, that it looks forward to proving them in court and may now file additional lawsuits.

The company released a letter from its chief executive Darl McBride to Szulik which stated that Red Hat's decision to file legal action "does not seem conducive to the long-term survivability of Linux".

It added that SCO would prepare a legal response that is likely to include counterclaims for copyright infringement and conspiracy.

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