From the 'aaaaaah that's why they hired those guys' file:

In March of this year Red Hat expanded its legal firepower by hiring lawyers Rob Tiller and Richard Fontana.  Three months later it's evident that these two have been busy as today Red Hat announced that it has settled two of three outstanding patent lawsuits.

"We're putting the patent issue to rest with the settlement of patent litigation involving Firestar Software, Inc. and DataTern Inc. that provides broad protections not only for Red Hat customers, but for the larger open source community, " Red Hat spokesperson Kerrin Catallozzi wrote in an email to InternetNews.com.

The Firestar and DataTern patent lawsuits date back to 2006 and alleged violation of U.S. Patent No. 6,101,502 which details a method for interfacing an object oriented application with a relational database. The suit pertained specifically to the JBoss Hibernate technology.

According to a Red Hat FAQ on the settlement:

Under the settlement, customers receive a license that grants a perpetual, fully paid-up, royalty-free, irrevocable worldwide license to the patents in suit to engage in any and all activities with respect to Red Hat products. Customers also receive a perpetual covenant not to sue with regard to all of DataTern's and Amphion's other patents on claims related to Red Hat products. The settlement will therefore provide a defense that should prevent DataTern and Amphion from bringing similar suits against any Red Hat customer based on use of a Red Hat product.

Red Hat has not yet publicly disclosed any financial terms of the patent settlement or even if there is any money changing hands as a result of this settlement. All we know for sure is that this issue is settled for Red Hat and for anyone (commercial or community user) that uses the technology in question.

Though Red Hat has now lifted some of the cloud of patent doubt for users, issues still remain. For one, the October 2007 patent lawsuit filed by IP Innovation LLC is still outstanding. That claim alleges that the Linux vendors are infringing on its U.S. Patent No. 5,072,412. The patent, originally issued Dec. 10, 1991, describes a "User Interface with Multiple Workspaces for Sharing Display System Objects.

Then of course there is Microsoft.

To date Microsoft has never formally filed a patent lawsuit against Red Hat, though Microsoft CEO Steve Ballmer has implied that Red Hat users should 'pay up'.