An Overview of Open-Source Software Licenses and the Value of Open-Source Software to Public Health Initiatives Erin N. Hahn he use of open-source software (OSS) has dramatically increased in the past several years, particularly in the public health domain. The Johns Hopkins Uni- versity Applied Physics Laboratory’s (APL) work on developing and licens- ing OSS identified a need within the public health community to better understand the definition and connotations of the words open source and the various open-source licenses. The use of OSS in the public health domain can dramatically improve the implementation of mobile and electronic health initiatives in resource-limited settings because OSS provides an affordable alternative to costly proprietary software. INTRODUCTION The term open source generally refers to software that In the past several years, the use of OSS in the public is made readily available by an individual or group for health field has grown dramatically. In particular, the others to use, modify, or redistribute under a licensing field of mobile health, or mHealth, has seen a substantial agreement with very few restrictions. Anyone can use increase in the use of OSS due to the ubiquitous nature the software without having to pay royalties or negoti- of cellular telephones.3 By definition, mHealth refers to ate a license agreement. Open-source software (OSS) is “the practice of medicine and public health, supported by not a new creation, but it has been used with increasing mobile devices.”4 In general, it involves the use of “mobile popularity in large-scale commercial software projects in communication devices, such as mobile phones and recent years. It has been called “the software that runs PDAs, for health services and information.”5 Many of the Internet,” referring to its significant use in the Inter- these platforms and associated tools, whose primary users net’s infrastructure, including the Apache Web server, are those in the field of public health or clinical care, the Mozilla browser, and Linux operating system.1 There are purportedly open source. However, in a community are currently at least 50 different open-source licenses, that is generally not as savvy in information technology, and they represent a unique approach to licensing when the term open source is confusing and leaves many unan- compared with licenses normally used in a commer- swered questions. The Johns Hopkins University Applied cial environment. (See Table 1 for a listing of licenses Physics Laboratory (APL), in conjunction with the Global by name.2) Emerging Infections Surveillance and Response System, 690 JOHNS HOPKINS APL TECHNICAL DIGEST, VOLUME 32, NUMBER 4 (2014) a division of the U.S. Armed Forces Health Surveillance has the right to change the source code. The term copyleft Center (AFHSC-GEIS), has been working to develop and was generated by the free software community and is the deploy open-source disease surveillance capabilities in term for a license condition that ensures that all modified resource-limited settings. In the course of this work, APL versions of the software can be copied, modified, and/or and AFHSC-GEIS identified a need to better understand distributed in the same way as the original. By ensuring the definition, nuances, and connotations of the term that downstream users receive source code and permis- open source within the public health community. sion to modify it, a copyleft license is said to keep code The purpose of this article is to provide an introduc- “forever free.”7 Not all open-source licenses have copyleft tion to open-source licensing and the main elements provisions, but many do. Despite what the name may to consider when determining whether to use OSS or imply, copyleft is still a license and is enforced by copy- when selecting an open-source license. In particular, it right law. Instead of withholding permission to copy or provides examples of the use of open-source licensing in modify a work (as in the traditional sense of a copyright), the development tools used in the public health domain. copyleft uses copyright law to actually require that those This article also provides background on copyright and permissions be granted. the distinction between a copyright and a license, a dis- It is important to note that using an open-source cussion of the history of open source and “free software” license is not the same as placing the software in the (terms that are often used interchangeably and also fre- public domain. The terms of the open source license quently consolidated and referred to as FOSS, or Free and must be met, and the copyright holder retains rights to Open-Source Software), and an overview of commonly the work. If the terms of the open-source license are not used licenses with strong user communities. It also dis- met (e.g., the same licensing provisions are not applied to cusses several myths related to the benefits and hazards of derivative works), the copyright has been infringed and using open-source licenses and OSS and provides exam- the copyright holder has certain legal remedies available ples of how government agencies are confronting these to him or her.5 No matter how permissive the open-source myths and successfully using OSS to their advantage. license, the copyright holder’s interests are protected. If the software is released into the public domain, the author surrenders the copyright. Put another way, as soon BACKGROUND ON COPYRIGHT as software code is created and saved, a copyright attaches Copyright is a form of intellectual property law and to the work. Placing the software in the public domain protects original works of authorship.5, 6 All software is relinquishes all rights associated with the work. It is not subject to copyright law, and as soon as source code is cre- equivalent to granting a license because the author is not ated, anyone (other the author) who wants to use it must limiting or placing restrictions on the use of the software obtain explicit permission from the author. (As soon as in any way. In fact, software placed in the public domain a work is created and “fixed in a tangible form that is can be used, modified, and removed from the public 5 perceptible either directly or with the aid of a machine domain by another user asserting copyright ownership. or device,” it is protected by copyright.1, 6, 7) Copyright is how an author retains control over his or her work. Software copyright is “the exclusive legal right to control FREE VERSUS OPEN SOFTWARE the rules for copying, modifying, and distributing a work The terms free software and open software are often of software.”7 The person or organization that has the used interchangeably, and they are also frequently con- right to control the work is called the copyright holder. solidated and referred to as FOSS. However, although a When copyright holders permit others to use, modify, or majority of software is both open and free, there are dis- distribute their software, they have granted a license.7 tinctions to be made between the two categories, both The license is the permission to use the software in some in philosophy and in the licenses that fall within each. way—it can be an unconditional grant of permission The free software movement is, at its roots, about the that mirrors the rights of the copyright holder or a con- users’ freedoms, whereas open source focuses on making ditional grant of permission that allows individuals to software better from a practical perspective by allowing copy or use the software according to certain provisions. access to the code so that others to improve it. These Open-source licenses fall into both categories. two views may lead to the same outcome in how the A general commercial copyright license usually pro- software is treated from a copyright perspective, but the tects the copyright holder’s interests by placing restric- goals for getting to that outcome are slightly different. tions on how the software can be used. For example, a (For a comprehensive overview of free software and commercial software license usually prohibits the copying OSS, see Ref. 8.) or modification of the software, mainly by distributing The concept of free software began in 1984 with only the machine-readable binary or object code. OSS Richard Stallman, a Massachusetts Institute of Tech- licenses give users more rights than a general commercial nology (MIT) researcher. Stallman was concerned that license because the user gets access to the source code and computing would be dominated by a few powerful people JOHNS HOPKINS APL TECHNICAL DIGEST, VOLUME 32, NUMBER 4 (2014) 691 E. N. HAHN if software were all proprietary. He considered software “1. Free Redistribution. The license shall not restrict scientific knowledge that should be shared and distrib- any party from selling or giving away the software as uted to further innovation in computer science. In 1984, a component of an aggregate software distribution he left MIT and began the GNU Project and the Free containing programs from several different sources. Software Foundation (GNU is a recursive acronym for The license shall not require a royalty or other fee “GNU’s Not Unix”). One goal of the GNU Project was for such sale. the development of a freely available operating system 8 2. Source Code. The program must include source that could run GNU software. code, and must allow distribution in source code as The most important characteristic of free software is well as compiled form. Where some form of a prod- the underlying philosophy for why software should be uct is not distributed with source code, there must be free and what free means.