Behind a scientific finding, in addition to unique data, there is often unique software. If Dryad archives data in part to allow others to validate the findings reported in the literature, then should we not also enable researchers to archive the software that was used to process, analyze and, in the case of simulations — create those data?
Some users have already deposited software source code alongside their data (e.g. doi:10.5061/dryad.8384, doi:10.5061/dryad.18) . If users are willing and able to release their code under a CC-Zero waiver , then there is nothing stopping this practice. In fact, Creative Commons and the Free Software Foundation have recently stated that CC-Zero is appropriate for release of software to the public domain .
Yet, a number of journal partners and users have requested that Dryad provide more, or different, options for software, and that authors should not be required to waive legal rights with CC-Zero. Since software is clearly a creative work, source code unambiguously carries copyrightable intellectual property. Enabling a greater range of licensing options could open the door to more authors archiving software that is integral to their paper, and this would further Dryad’s mission of enabling scientists to validate and build upon previously work. So, how should we do that?
One important consideration is that we aim to make the submission process as easy as possible for users. This would be compromised by presenting a confusing array of licensing options, and having those differ between types of files.
The principle desiderata of a license for deposited software are more or less the same as for data: freedom to reuse, modify (analogous to the “recombine” for data), and redistribute (in original or modified form), with no more than attribution expected or required. It turns out that these are also the principles common to all licenses approved by the Open Source Initiative, or OSI .
So, could we just pick one of the minimally restrictive OSI-approved licenses (since we want to facilitate reuse rather than hamper it), and require release of software under those terms? We are currently of the opinion that the answer is “no”, for a couple of reasons:
(1) Some, though not all, software will already be licensed. Asking a user to choose a different one would clearly be a burden, since changing a license requires express consent from all copyright holders, including possibly the employer or funder.
(2) If the software includes third-party code to which a ‘share-alike’ license has been assigned (e.g. the GNU Public License, or GPL ) , then the user is required to release the code under equivalent licensing terms. Unlike for data, it would be highly unusual to combine software source code from many different sources, and so this does not pose an insurmountable barrier to archiving and reuse for scientific purposes.
Given the above, our current thinking is that Dryad should enable users to select any OSI-approved license they deem appropriate. However, we also wish to strongly guide users, when there is no prior license assigned to any part of their software, to choose either a non-share alike OSI license or a CC-Zero waiver. It is currently unclear whether dedicating software to the public domain with CC-Zero would be of as much value as it is for data . We’d welcome your thoughts on that.
There are some other considerations on our plate, as well:
- We want to be careful to avoid steering users away from using a public source code repository when that is more appropriate . Is it better for Dryad to host code snapshots, or to direct users to specific versions of software in a public code repository?
- Some users bundle software and data together in tarballs or zip archives. Since we cannot easily assign different terms to the data and software within such a combined file, it could increase the burden on users to separate these components out.
- In addition to software, there is other content that publishers host in Supplemental Materials that some of our partner journals would like Dryad to host, instead. To the extent that some of this content is neither data nor software, should we be recognizing a third category of intellectual property, to which a license such as CC-BY  would be assigned?
If you have opinions or ideas, we would like to encourage you to share them with us as public comments on this blog. What’s the best way to accommodate software (and other non-data material) within Dryad?
 Some software source code in Dryad is already available under grandfathered license terms, such as in doi:10.5061/dryad.18.
 Dryad currently requires users to assign CC-Zero to all archived files. This waives all copyright and related rights in the data (to the extent legally possible in an author’s jurisdiction), effectively dedicating the data to the public domain. The use of CC-Zero is predicated on most data being “facts”, and facts in most jurisdictions cannot be copyrighted, although this not universally true (e.g. photographs). Note that Dryad has a policy that the original article and the data package are to be cited when the data are reused, but we feel that this is most appropriately enforced through scholarly practice, not through a license.
 According to Creative Common’s FAQ, CC-Zero “is suitable for dedicating your copyright and related rights in computer software to the public domain, to the fullest extent possible under law. Unlike CC licenses, which should not be used for software, CC0 is compatible with many software licenses, including the GPL“.
 For the motivation behind the recommended use of CC-Zero for data, see the Science Commons Protocol for Implementing Open Access Data
 Public open source code repositories include generic ones, such as Sourceforge, as well as those specific to particular types of code, such as R-forge for R, and CPAN for Perl. For more about best practices in scientific software development, see Baxter SM, Day SW, Fetrow JS, Reisinger SJ (2006) Scientific Software Development Is Not an Oxymoron. PLoS Comput Biol 2(9): e87. doi:10.1371/journal.pcbi.0020087
 Many thanks to H. Lapp for starting this post. I (T. Vision) take responsibility for the opinions expressed here, as well as any sins of omission or commission.