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Licensing Astrophysics Codes Session at AAS 225

Friday, February 20, 2015 - 10:50

This post originally appeared on

On Tuesday, 6 January, at the 225th AAS meeting in Seattle, Washington, the Astrophysics Source Code Library (ASCL), AAS Working Group on Astronomical Software (WGAS), and Moore-Sloan Data Science Environment at New York University (NYU) sponsored a special session on software licenses, with support from the AAS. This subject was suggested as a topic of interest in the Astrophysics Code Sharing II: The Sequel session held at the 223rd meeting of the AAS in 2014.

Frossie Economou from the Large Synoptic Survey Telescope (LSST) and chair of the WGAS stressed the importance of licensing; Alice Allen, editor of the ASCL, gave a 90-second overview of the ASCL; and Alberto Accomazzi from the SAO-NASA Astrophysics Data System (ADS) moderated the open discussion (opening slides). The panel of six speakers discussed different licenses and shared considerations that arise when choosing a license; they also covered institutional concerns about intellectual property, governmental restrictions on exporting codes, concerns about software beyond licensing, and information on how much software is licensed and characteristics of that software.

photo of audience at licensing session

Discussion period moderated by Alberto Accomazzi

Main Presentation Points:

  • Copy-left and Copy-right, Jacob VanderPlas (eScience institute, University of Washington)
    Jake extolled everyone to always license codes, as in the US, copyright law defaults to “all privileges retained” unless otherwise specified. He pointed out that “free software” can refer to the freedoms that are available to users of the software. He covered the major differences between BSD/MIT-style “permissive” licensing and GPL “sticky” licensing while acknowledging that the difference between them can be a contentious issue.
    slides (PDF)
  • University Tech Transfer Perspective on Software Licensing, Laura L. Dorsey (Center for Commercialization, University of Washington)
    Universities care about software licenses for a variety of reasons, Laura stated, which can include limiting the university’s risk, respecting IP rights, complying with funding obligations, and retaining academic and research use rights. She also covered factors software authors may care about, among them receiving attribution, controlling the software, and making money. She reinforced the importance of licensing code and discussed the common components of a software license.
    slides (PDF)
  • Relicensing the Montage Image Mosaic Engine, G. Bruce Berriman (Infrared Processing and Analysis Center, Caltech)
    In last year’s Astrophysics Code Sharing session, Bruce had discussed the limitations of the Caltech license under which the code Montage was licensed; since then, Montage has been relicensed to a BSD 3-Clause License. Following on the heels of Laura’s discussion and serving as a case study for institutional concerns regarding software, Bruce related the reasons for and concerns about the relicensing, and discussed working with the appropriate office at Caltech to bring about this change.
    slides (PDF)
  • Export Controls on Astrophysical Simulation Codes, Daniel Whalen (Institute for Theoretical Astrophysics, University of Heidelberg)
    image of presentation slide

    Restricted algorithms; image: Adam M. Jacobs

    Dan’s presentation covered some of the government issues that arise from research codes, including why certain codes fall under export controls; a primary reason is to prevent the development of nuclear weapons. Dan also brought up how foreign intelligence agencies collect information and what specific simulations are restricted, and stated that federal rules are changing, but slowly.
    slides (PDF)

  • Why Licensing Is Just the First Step, Arfon M. Smith (GitHub Inc.)
    Arfon went beyond licensing in his presentation to discuss open source and open collaborations, and how GitHub delivers on a “theoretical promise of open source.” He shared statistics on the growth of collaborative coding using GitHub, and demonstrated how a collaborative coding process can work and pointed out that through this exposed process, community knowledge is increased and shared. He challenged the audience to contemplate the many reasons for releasing a project and to ask themselves what kind of project they want to create.
    slides (PDF)
  • Licenses in the Wild, Daniel Foreman-Mackey (New York University)
    First, I have to note that Dan made it through 41 slides in just over the six minutes allotted for his talk, covering about seven slides/minute; I don’t know whether to be more impressed with his presentation skills or the audience’s information-intake abilities!
  • 17% of GitHub repositories examined are licensed

    Percentage of licensed GitHub repos; image: Arfon Smith

    After declaring that he knows nothing about licensing, Dan showed us, and how, that he knows plenty about mining data and extracting information from it. From his “random” selection of 1.6 million GitHub repositories, he noted with some glee that 63 languages are more popular on GitHub than IDL is, the number of repositories with licenses has increased since 2012 to 17%, and that only 28,972 of the 1.6 million mentioned the license in the README file. Dan also determined the popularity of various licenses overall and by language and shared that information as well.
    slides (PDF)

Open Discussion Takeaway Points:

  • Discuss licensing with your institution; it’s likely there is an office/personnel devoted to deal with these issues.
  • This office is likely very familiar with issues you bring to it, including who to refer you to when the issues are outside their purview.
  • “Friends don’t let friends write their own licenses.” IOW, select an existing license rather than writing your own.
  • License your code.
  • Let others know how you want your code cited/acknowledged.


Many resources on licensing, including excellent posts by Jake and Bruce, can be found on

Alice Allen
Editor, Astrophysics Source Code Library
Astrophysics Source Code Library
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