requires non-disclosure of the code and claim that all code developed by UNIX licensees that is used with the code under license be held in confidence. This claim is discussed above at Control of derivative works. SCO and the GPL Before changing their name to the SCO Group, the company was known as Caldera International. Caldera was one of the major distributors of Linux between 1994 and 1998. In August 1998, the company split into Caldera Systems and Caldera Thin Clients, with Caldera Systems taking over the Linux systems business and Caldera Thin Clients concentrating on the Thin Clients and embedded business. The parent and shell company Caldera, Inc. ceased to exist in 2000 after a settlement with Microsoft in the Caldera v. Microsoft lawsuit. Caldera Systems was reorganized to become Caldera International in 2001, the company, which was renamed to The SCO Group in 2002. Some, like Eben Moglen, have suggested that because Caldera distributed the allegedly infringing code under the GNU General Public License (GPL), that this act would license any proprietary code in Linux. SCO has stated that they did not know their own code was in Linux, so releasing it under the GPL does not count. However, as late as July and August 2006, long after that claim was made, they were still distributing ELF files (the subject of one of SCO's claims regarding SVRx) under the GPL. SCO has also claimed, in early stages of the litigation, that the GPL is invalid and non-binding and legally unenforceable. In response, supporters of the GPL, such as Eben Moglen, claimed that SCO's right to distribute Linux relied upon the GPL being a valid copyright license. Later court filings by the SCO Group in SCO v. IBM use SCO's alleged compliance with the license as a defense to IBM's counterclaims. The GPL has become an issue in SCO v. IBM. Under U.S. copyright law, distribution of creative works whose copyright is owned by another party is illegal without permission from the copyright owner, usually in the form of a license; the GPL is such a license, and thus allows distribution, but only under limited conditions. Since IBM released the relevant code under the terms of the GPL, it claims that the only permission that SCO has to copy and distribute IBM's code in Linux is under the terms and conditions of the GPL, one of which requires the