Suddenly all those discussions about the discordant ways of open-source software and patent law have become a lot less abstract.

Companies called IP Innovation and Technology Licensing Corporation sued Red Hat and Novell on Tuesday, claiming the top Linux sellers' software products infringe U.S. patent 5,072,412, "User interface with multiple workspaces for sharing display system objects," and two identically named patents. The suit (PDF), in the U.S. District Court in Eastern Texas, seeks damages and a permanent injunction prohibiting any further infringement.

Red Hat spokeswoman Leigh Day said Friday only that the company is aware of the suit and "will review the situation." Novell spokesman Bruce Lowry said the company is assessing the suit and that "it's too early to tell, tactically, whether it makes sense for us and Red Hat to join forces."