Intellectual property licensing firms IP Innovation and Technology Licensing Corporation have filed a lawsuit against Red Hat and Novell for alleged patent infringements in their Linux distributions.

The legal case is the first patent challenge against Linux distributors in court, and concerns patent numbers 5,072,412, 5,533,183 and 5,394,521.

All three describe a "user interface with multiple workspaces for sharing display system objects" and were issued between December 1991 and February 1995.

The suit was filed on 9 October in the district court of Eastern Texas, where judges are known to favour patent owners.

The plaintiffs demand an injunction prohibiting Novell and Red Hat from continuing to infringe the three patents, as well as unspecified damages.

Novell and Red Hat have indemnification clauses in their user agreements, vowing to protect end users from such claims. Users can therefore trust that they will not be affected by the suit.

A Novell spokesperson said that the firm is evaluating its options and vowed to defend its interests. Red Hat did not immediately respond to a request for comment.