On Tuesday, January 6, the ASCL, AAS Working Group on Astronomical Software (WGAS), and the Moore-Sloan Data Science Environment at 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 at AAS 223.

Frossie Economou from the LSST and chair of the WGAS opened the session with a few words of welcome and stressed the importance of licensing. I gave a 90-second overview of the ASCL before turning the podium over to Alberto Accomazzi from NASA/Astronomy Data System (ADS), who introduced the panel of speakers and later moderated the open discussion (opening slides), after which Frossie again took the podium for some closing remarks. 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. The floor was then opened for discussion and questions.

Discussion period moderated by Alberto Accomazzi

Presentations
Some of the main points from each presentation are summarized below, with links to the slides used by the presenters.

• • 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)
    

    Restricted algorithms; image by 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!
    

    Percentage of licensed GitHub repos; image by 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 have 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
After Dan’s presentation, Alberto Accomazzi opened the floor for discussion. Takeaway points included:

• 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

My thanks to David W. Hogg, Kelle Cruz, Matt Turk, and Peter Teuben for work — which started last March! — on developing the session, to Alberto for his excellent moderating and to Frossie for opening and closing it. My thanks also to the wonderful Jake, Laura, Bruce, Dan W, Arfon, and Dan F-M for presenting at this session, and to the Moore-Sloan Data Science Environment at NYU and AAS for their sponsorship.

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