I have already written about software licensing a few weeks ago. This week, I want to write about about a paper by Morin, Urban and Sliz, who wrote a primer on software licensing, with the goal of helping scientists engage better with their institutional Technology Transfer Offices (TTO’s) when choosing licenses. Morin and Sliz are biologists at UC Berkeley, and Urban is a lawyer, also at Berkeley. The paper was published in PloS Computational Biology, July 2012, Vol 8, Issue 7. e1002598, and can be downloaded free of charge.
I recommend this paper for anyone embarking on the task of licensing their software. I wish I had read this paper before I had started working on relicensing Montage! The paper outlines why you should license your software, summaries the types of licenses available and the pros and cons of them, and explains the benefits of software licenses in the era of an open culture.
A license is a contract between the rights’ owner of the software (the author or, most likely, their institution) and the end-user, and states the conditions under which the end-user may use the software. There are three types of license: proprietary, free and open source (FOSS) and hybrid. Table 1 from the paper summarizes them:
Proprietary licenses restrict usage according to the issue’s business strategies, and are usually restrictive and customized (“bespoke”). FOSS licenses, in contrast, aim to minimize barriers to software use and dissemination. These licenses are non-discriminatory – that is, anyone, including commercial companies, can use them. Hybrids are a combination of the two, invariably bespoke, and are uncommon because applying them can be costly.
The paper gives a clear summary of the terms and concepts in licensing. Open source licenses “require the source code be available to users, and that users be able to reuse, modify, and distribute the code” and have the primary benefit of encouraging a user community. The terms “Permissive” and “copyleft” compare legal philosophies of FOSS licenses. Permissive licenses place fewest restrictions on use of the code, whereas copyleft licenses require that any derivative works also be distributed under the same licensing terms as the original – the benefit of this approach is that it guarantees perpetual open access. Fig 1 (Fig 2 in the paper) below summarizes the directionality of permissive and copyleft licenses:
Perhaps the most useful part of the paper is a guide to when to use each type of license, and I will quote verbatim here:
“If you want…
…the widest possible distribution and adoption, fewest restrictions on users, open and transparent source code, peer review, community contributions to the codebase, and easy incorporation of your code by others… then a permissive FOSS license such as the BSD/MIT, Apache, or ECL licenses may work well
…to assure the benefits and openness of FOSS in all future derivatives of your work, open and transparent source code, peer review, community contributions to the codebase, and the potential incorporation of your code into other copyleft- licensed works… then you should consider a copyleft FOSS license like the GPL, LGPL, or MPL.
the ability to separately pursue proprietary models while leveraging the wide distribution, adoption, community contributions, and other benefits of open source software… then a hybrid or multi-license scheme may be ap-propriate.
…protect the confidentiality of your source code, reserve maximum control over the distribution and use of your software, and derive licensing revenue… then you should consider a proprietary license.”