2018-06-19 05:06:22 +00:00
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% Copyright (C) 2018, Bradley M. Kuhn
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% License: CC-BY-SA-4.0
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2018-06-19 03:04:06 +00:00
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\documentstyle[twocolumn]{article}
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\pagestyle{empty}
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\begin{document}
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%don't want date printed
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\date{}
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%make title bold and 14 pt font (Latex default is non-bold, 16 pt)
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\title{\Large\bf A Comprehensive Consideration of Installation Requirements of the GPL}
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%for two authors (this is what is printed)
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\author{\begin{tabular}[t]{c@{\extracolsep{8em}}c@{\extracolsep{8em}}c}
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Bradley M. Kuhn & Behan Webster \\
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Software Freedom Conservancy, Inc. & Converse In Code
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\end{tabular}
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}
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\thispagestyle{empty}
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\maketitle
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\subsection*{\centering Abstract}
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The GNU General License (``GPL'') is the most widely used \textit{copyleft}
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license for software. Copyleft licenses function as copyright license in
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atypical manner: rather than restricting permission to copy, modify and
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redistribute the software, copyleft licenses encourage and enable such
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activities. However, these license have strict requirements that mandate
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further software sharing by enabling downstream users to easily improve,
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modify, and upgrade the copylefted software on their own.
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GPL has two versions in common use: version 2 (``GPLv2'') and version 3
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(``GPLv3''). Both versions require those who redistribute the software to
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provide information related to the installation of software modified by
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downstream. These installation requirements, however, differ somewhat in
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their details. While some business practices around license compliance
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efforts have reached adequate sophistication to address simpler compliance
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problems, firms have generally given inadequate attention to the installation
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requirements of both common versions of GPL\@. Misunderstanding of these
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clauses is often common, and violations related to installation instructions
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remain prevalent.
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Furthermore, perceived differences in the requirements, and lack of rigorous
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study of the Installation Information requirements of GPLv3\S6 has allowed
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rumor and impression, rather than a textually grounded adherence to the
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written rules, to govern industry response in adoption of software licensed
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under GPLv3. The resulting scenario often causes redistributors to assume
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the GPLv2 has \textbf{no} requirements regarding installation information,
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and that GPLv3's requirements in this regard are impossible to meet,
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particularly in security-conscious embedded products.
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This paper explores the installation provisions of both common versions of
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GPL, discusses historical motivations and context for each, and suggests best
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practices regarding installation information for firms that redistribute
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software under both licenses.
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2018-06-19 05:06:22 +00:00
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\section{Introduction}
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Free, Libre and Open Source (``FLOSS'') licenses are typically categorized as
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either copyleft or non-copyleft licenses. The license compliance demands of
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most non-copyleft licenses typically center purely around issues of author
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attribution, and thus are straightforwardly addressed by license compliance
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programs such as OpenChain and SPDX, which focus on the details of properly
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annotating licensing information for software in the supply-chain to assure
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proper downstream license and related author credit notification.
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Copyleft licenses do indeed require proper downstream license and credit
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notification, and thus we can broadly model copyleft license requirements as
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a proper superset of those requirements of non-copyleft licenses. The
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compliance subset of license annotation is a well-studied problem, and many
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automation tools exist and remain under active development to assist in these
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aspects of compliance. Unfortunately, the nascent state of industry
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compliance efforts currently means that firms are often ill-equipped to
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handle the additional requirements of copyleft licenses.
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In particular, software copyleft licenses are specifically designed to
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promulgate a transparent agenda to champion the rights of downstream users to
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effectively and easily copy, modify, reinstall and redistribute the software
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both commercially and non-commercially. Proper verification of source code
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for license compliance generally cannot be automated. Indeed, given that
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program equivalence (often colloquially called the ``Halting Problem'') was
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mathematically proven as an undecidable problem in the computing subfield of
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Theory of Computation, we know that a generalized solution that shows
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specific source code corresponds to a specific set of binaries remains
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unsolvable in the general case.
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We do expect automation tools that approximate solutions for the specific
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cases of most interest to adopter of copylefted software to eventually exist.
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Currently, much research and industry attention has turned toward the
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software engineering problem of ``reproducible builds''. We find this area
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of endeavor directly applicable to the requirements of copyleft license
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compliance, and believe that reproducible build techniques will eventually
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become as common for compliance with source code provisioning terms of
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FLOSS licenses as SPDX and OpenChain are for the license notice and
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attribution requirements are today.
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However, even that solution, when it exists, will not fully satisfy the goals
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of many firms. Frankly, most firms do not share the idealistic goals of
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software freedom activists who design copyleft licenses. These activists
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seek to defends the rights of software users by creating copyleft licenses
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that mandate source code provisioning, which include the rights to modify and
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install modified versions of the software. However, in what the inventor of
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copyleft, Richard M.~Stallman, called ``pragmatic idealism'', copyleft
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licenses make reasonable trade-offs regarding how much disclosure is required
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to downstream. While conventional wisdom often considered copyleft licenses
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to contain substantial and complicated requirements, ultimately the
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requirements are substantially more permissive than most industry-standard
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proprietary licenses, which often complete prohibit redistribution of the
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software and disclose absolutely no source code. Copyleft licenses typically
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make a clear compromise between maximal software freedom for the downstream
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recipient and permission for firms to distribute proprietary software in
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aggregation with copylefted software.
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By way of hypothetical counterexample, consider this possible ``copyleft''
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license that one might create:
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\begin{quotation}
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\begin{center}
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{\Large The Unreasonably Overly Broad Copyleft License}
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If you distribute this software in any form, you agree to publicly release
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the complete source code of all software that you and your successors in
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interest write, in any form, for perpetuity.
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\end{quotation}
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Besides likely being unenforceable for various reasons, firms would quickly
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ban all software under this license, and ban all employees from ever using
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such software at home or work. A highly broad license of this nature, even
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if succeeded in the very short term in a few instances, would fail long-term
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to reach the long term goal of maximizing software freedom for users.
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Copyleft, therefore, must find a balance between two competing goals:
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\begin{itemize}
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\item Ensure the rights to copy, share, modify, redistribute,
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and reinstall the software for downstream users.
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\item Entice firms that do not seek the same goals as the activists to adopt,
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share and improve the copylefted software to assure its promulgation.
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\end{itemize}
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In essence, much FLOSS licensing balances these competing goals.
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Non-copyleft licenses favor the latter much more than the former, and
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copyleft licenses seek to create an optimal policy between the ``maximal
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software freedom'' vs. ``adoption and popularity'' dichotomy, to assure that
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in the long term, users have these specific rights, but also allow for short
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term interest of firms and individuals alike who may not share the software
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freedom activist perspective.
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\section{Historical Background}
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Despite the awareness of copyleft activists, the adoption of copyleft
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licenses has been wrought with acrimony and accusation. To our knowledge,
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there are no specific empirical studies of attitudes and reasoning why firms
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initially rejected copyleft (and that some still do). However, consideration
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of anecdotes can illuminate study of the reasons why confusion exists
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regarding copyleft licensing requirements in general, and in particular
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(which will be the focus of this article) the installation requirements of
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the GNU General Public License (``GPL'').
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The Free Software Foundation (``FSF''), which is the license steward for all
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existing versions of the GPL, was the first to license software under GPL\@.
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Released in 1991, GPLv2 came into wide use by other software authors,
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including those of Linux. During the 1990s, the alternative body of software
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released under GPLv2 gained slow but steady adoption, until major firms could
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no longer ignore it.
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In 2001, Microsoft launched a series of political attacks against the GPL\@.
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Over a period of months, various Microsoft executives called the GPL
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``unAmerican'' and a ``cancer'' on the software industry. This was the first
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time most in the industry had ever heard of the GPL, and the rhetoric created
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the expected fervor.
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The industry context of the time was the growing adoption of GPL'd software,
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and Linux, in particular, by firms. While Microsoft was not the first to
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draw negative attention to GPL's copyleft provisions, but sadly the
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misunderstandings launched in these attacks remain with us today.
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Adoption of FLOSS grew quickly in the last two decades. License compliance
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and FLOSS supply-chain adoption techniques have become essential components
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of most large firms along with this adoption. However, these tools and
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procedures have focused on the straightforward problems of license notice,
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attribution, and supply-chain FLOSS inclusion discovery techniques. The
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finer points of copyleft license compliance, particularly source code
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provisioning and installation requirements of GPL, remain often
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misunderstood, and sometimes outright ignored.
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Historically, firms have often reacted to the two popular versions of the GPL
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in the same pattern. During the feverish anti-copyleft rhetoric of the
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1990s, firms widely considered the GPLv2 as a toxic license they could not
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abide. Eventually, executives and lawyers at major firms learned what their
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engineers often already knew: that GPLv2 was not unreasonable, its
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requirements were well understood and could be respected by businesses that
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produced both FLOSS and proprietary products.
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We now see the same process happening, albeit much more slowly, with GPLv3.
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We hear rhetoric drawing attention to perceived differences between GPLv2's
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and GPLv3's requirements, which seem untenable to firms, some of whom
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maintain GPLv2'd forks of projects that have moved on to the
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``GPLv3-or-later'' upstream.
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2018-06-19 03:04:06 +00:00
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\end{document}
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