Open-source software is one of the fastest-growing areas in the software industry. In the past decade, both the number of open-source projects and the total lines of open-source code have grown exponentially. Amit Deshpande & Dirk Riehle, "The Total Growth of Open Source," In Proceedings of the Fourth Conference on Open Source Systems (OSS 2008). In addition, the number of corporations employing open-source software has grown dramatically. A recent survey found that 85 percent of companies employ open-source software in their business. David Meyer, Gartner: 85 Percent of Companies Using Open Source, cnet. This rapid growth led the Federal Circuit Court of Appeals to note that "open-source licensing has become a widely used method of creative collaboration that serves to advance the arts and sciences in a manner and at a pace that few could have imagined just a few decades ago." Jacobsen v. Katzer, 535 F.3d 1373, 1378 (Fed. Cir. 2008). This substantial growth is in part attributable to the open-source community's increased use of reciprocal licensing agreements, sometimes referred to as copyleft agreements.
Copyleft agreements are used to control the availability of open-source software. The agreements are designed to allow a copyright holder to make a software program available to the public for no fee, while also requiring all modified and extended versions of the program to be freely available to the public. The intent of copyleft agreements is to prevent an individual from converting a freely available open-source program into proprietary software.