Before the open-source movement in the 1980s, almost all software was proprietary and did not disclose its
source code. Open-source licensing is intended to maximize openness and minimize barriers to software use, dissemination, and follow-on innovation. Open-source licenses share a number of key characteristics: • Free redistribution: Anyone can redistribute the software, for free or for cost, without the permission of or payment to the copyright holder. • Unrestricted, public access to the
source code—what the term
open source refers to • Users may modify the software and release
derivative works, either under the same terms as the free software or, in some cases, under a different license. • Nondiscrimination between different uses, including commercial use. The
Open Source Initiative vets and approves new open-source licenses that comply with its
Open Source Definition.
Types of open-source licenses (permissive), the
MIT License (permissive), and the
GPL (copyleft). • If software is in the
public domain, the owner's copyright has been extinguished and anyone may use the work with no copyright restrictions. • Non-restrictive licenses allow free reuse of the work without restrictions on the licensing of
derivative works. Many of them require attribution of the original creators. The first open-source license was a non-restrictive license intended to facilitate scientific collaboration: the
Berkeley Software Distribution (BSD), named after the
University of California, Berkeley in 1978. •
Copyleft licenses (also known as "share-alike"), require
source code to be distributed with software and require the source code be made available under a similar license. Copyleft represents the farthest that reuse can be restricted while still being considered free software. Strong copyleft licenses, such as the
GNU General Public License (GPL), allow for no reuse in proprietary software, while weak copyleft, such as the related
GNU Lesser General Public License (LGPL), do allow reuse in some circumstances. Copyleft licenses are perceived by developers as a way of ensuring that their contributions do not create unfair advantages for others. Another motivation for choosing copyleft is to promote open source through its requirements for derivative works:
Stallman states that "the central idea of copyleft is to use copyright law, but flip it over to serve the opposite of its usual purpose: instead of a means of privatizing software, [copyright] becomes a means of keeping software free." Outside of software, noncommercial-only
Creative Commons licenses have become popular among some artists who wish to prevent others from profiting excessively from their work. However, software that is made available for
noncommercial use only is not considered open source.
Sun Microsystems' noncommercial-only
Java Research License was rejected by the open-source community, and in 2006 the company released most of Java under the GPL.
Compatibility Since 1989, a variety of
open-source licenses for software have been created. Choosing an open-source software license has grown increasingly difficult due to the
proliferation of licenses, many of which are only trivially distinct. Many licenses are incompatible with each other, hampering the goals of the free software movement. Translation issues, ambiguity in licensing terms, and incompatibility of some licenses with the law in certain jurisdictions compounds the problem. Although downloading an open-source module is quick and easy, complying with the licensing terms can be more difficult. The amount of software dependencies means that engineers working on complex projects must often rely on software license management software in order to help them achieve compliance with the licensing terms of open-source components. Many open-source software files do not unambiguously state the license, increasing the difficulties of compliance. When combining code bases, the original licenses can be maintained for separate components, and the larger work released under a compatible license. This compatibility is often one-way. Public domain content can be used anywhere as there is no copyright claim, but code acquired under almost any set of terms cannot be waved to the public domain. Permissive licenses can be used within copyleft works, but copyleft material cannot be released under a permissive license. Some weak copyleft licenses can be used under the GPL and are said to be GPL-compatible. GPL software can only be used under the GPL or AGPL.
Enforceability Free and open-source software licenses have been successfully
enforced in civil court since the mid-2000s. Courts have found that distributing software indicates acceptance of the license's terms. However, developers typically achieve compliance without lawsuits.
Social pressures, such as the potential for community backlash, are often sufficient.
Cease and desist letters are a common method to bring companies back into compliance, especially in Germany. A long-debated subject within the FOSS community is whether open-source licenses are "bare licenses" or
contracts. A bare license is a set of conditions under which actions otherwise restricted by
intellectual property laws are permitted. Under the bare license interpretation, advocated by the
Free Software Foundation (FSF), a case is brought to court by the copyright holder as
copyright infringement. Under the contract interpretation, a case can be brought to court by an involved party as a
breach of contract. United States and French courts have tried cases under both interpretations.
Value More than 90 percent of companies use open-source software as a component of their proprietary software. The decision to use open-source software, or even engage with open-source projects to improve existing open-source software, is typically a pragmatic business decision. When proprietary software is in direct competition with an open-source alternative, research has found conflicting results on the effect of the competition on the proprietary product's price and quality. For decades, some companies have made servicing of an open-source software product for enterprise users as their business model. These companies control an open-source software product, and instead of charging for licensing or use, charge for improvements, integration, and other servicing.
Software as a service (SaaS) products based on open-source components are increasingly common. Open-source software is preferred for scientific applications, because it increases transparency and aids in the validation and acceptance of scientific results. == See also ==