■ R i c h a r d L i n 林 旅 強 (legist 強 ) ■ [email protected]■ http://about.me/richard.lin ■ http://fb.me/legist These slides are licensed under creative commons - attribution - share alike 3.0 unported. Hong Kong Open Source Conference 2014 香港開源年會 2014/3/29 Sat. The Rules of Open Source and Collaboration: Copyright and Public License
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The Rules of Open Source and Collaboration: Copyright and Public License
The Rules of Open Source and Collaboration: Copyright and Public License
Collaboration is the most important feature of open source. However, does the collaborative output belongs to public property (in the public domain) and allow anyone to be able to use without restriction? In other words, could the original project owner control the subsequent use of these results by others? These issues are referred to how the original game rules be established. This lecture will overview the rules of open source collaboration within legal framework from the default rule of copyright law and the mechanism design of different open source licenses.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
■ The world without software copyright■ Richard M. Stallman and Xerox Printer
■ After we have software copyright■ 1980s■ Business model
呵呵(Fake Dialogue)
( 設計對白 )
What the F...
● The world w ithout software copyright● Richard M . Stallman and Xerox Printer
● After we have software copyright● 1980s● Business model
(Fake dialogue)( 設計對白 )
CopyrightCopyright
■ The world without software copyright■ Richard M. Stallman and Xerox Printer
■ After we have software copyright■ 1980s■ Business model
■ Richard M. Stallman: Free Software!
Free SoftwareFree Software
■ Free Software■ Free Software Foundation (FSF) 1985-■ Fundamentalism
Free SoftwareFree Software
■ Free Software■ Free Software Foundation (FSF) 1985-■ Fundamentalism■ GNU Project
GNU's Not Unix
Free SoftwareFree Software
■ Free Software■ Free Software Foundation (FSF) 1985■ Fundamentalism■ GNU Project■ GNU General Public License
Free Software DefinitionFree Software Definition
■ The freedom to run the program, for any purpose
(freedom 0).
■ The freedom to study how the program works, and
change it to make it do what you wish (freedom 1).
■ The freedom to redistribute copies so you can help your
neighbor (freedom 2).
■ The freedom to distribute copies of your modified
versions to others (freedom 3). By doing this you
can give the whole community a chance to benefit from your changes.
Run the Program
Free Software DefinitionFree Software Definition
■ The freedom to run the program, for any purpose
(freedom 0).
■ The freedom to study how the program works, and
change it to make it do what you wish (freedom 1).
■ The freedom to redistribute copies so you can help your
neighbor (freedom 2).
■ The freedom to distribute copies of your modified
versions to others (freedom 3). By doing this you
can give the whole community a chance to benefit from your changes.
Study & Change
Free Software DefinitionFree Software Definition
■ The freedom to run the program, for any purpose
(freedom 0).
■ The freedom to study how the program works, and
change it to make it do what you wish (freedom 1).
■ The freedom to redistribute copies so you can help your
neighbor (freedom 2).
■ The freedom to distribute copies of your modified
versions to others (freedom 3). By doing this you
can give the whole community a chance to benefit from your changes.
Redistribute
Free Software DefinitionFree Software Definition
■ The freedom to run the program, for any purpose
(freedom 0).
■ The freedom to study how the program works, and
change it to make it do what you wish (freedom 1).
■ The freedom to redistribute copies so you can help your
neighbor (freedom 2).
■ The freedom to distribute copies of your modified
versions to others (freedom 3). By doing this you
can give the whole community a chance to benefit from your changes.
Distribute copiesof modified version
The Free Software DefinitionThe Free Software Definition
■ The freedom to run the program, for any purpose
(freedom 0).
■ The freedom to study how the program works, and
change it to make it do what you wish (freedom 1).
■ The freedom to redistribute copies so you can help your
neighbor (freedom 2).
■ The freedom to distribute copies of your modified
versions to others (freedom 3). By doing this you
can give the whole community a chance to benefit from your changes.
散佈 Distribute
修改 Modify
研究 Study
使用 Run
The Free Software DefinitionThe Free Software Definition
■ The freedom to run the program, for any purpose
(freedom 0).
■ The freedom to study how the program works, and
change it to make it do what you wish (freedom 1).
■ The freedom to redistribute copies so you can help your
neighbor (freedom 2).
■ The freedom to distribute copies of your modified
versions to others (freedom 3). By doing this you
can give the whole community a chance to benefit from your changes.
散佈 Distribute
修改 Modify
研究 Study
使用 Run
How aboutPublic Domain?
How to protect the freedom?How to protect the freedom?
■ Public Domain allows people to share the program and their improvements, if they are so minded. But it also allows uncooperative people to convert the program into proprietary software.
■ People who receive the program in that modified form do not have the freedom that the original author gave them; the middleman has stripped it away.
How to protect the freedom?How to protect the freedom?
■ Public Domain allows people to share the program and their improvements, if they are so minded. But it also allows uncooperative people to convert the program into proprietary software.
■ People who receive the program in that modified form do not have the freedom that the original author gave them; the middleman has stripped it away.
Public Domaincan be transferred
to Proprietaryeasily.
Public Domaincan not make surethe four freedoms
keep going.
How to protect the freedom?How to protect the freedom?
■ Public Domain allows people to share the program and their improvements, if they are so minded. But it also allows uncooperative people to convert the program into proprietary software.
■ People who receive the program in that modified form do not have the freedom that the original author gave them; the middleman has stripped it away.
Public Domaincan be transferred
to Proprietaryeasily.
Public Domaincan not make surethe four freedoms
keep going.
Public Domainis an option for
copyright holder todecide how his/her work can be usedby other people.
The Free Software DefinitionThe Free Software Definition
■ The freedom to run the program, for any purpose
(freedom 0).
■ The freedom to study how the program works, and
change it to make it do what you wish (freedom 1).
■ The freedom to redistribute copies so you can help your
neighbor (freedom 2).
■ The freedom to distribute copies of your modified
versions to others (freedom 3). By doing this you
can give the whole community a chance to benefit from your changes.
The Free Software DefinitionThe Free Software Definition
■ The freedom to run the program, for any purpose
(freedom 0).
■ The freedom to study how the program works, and
change it to make it do what you wish (freedom 1).
■ The freedom to redistribute copies so you can help your
neighbor (freedom 2).
■ The freedom to distribute copies of your modified
versions to others (freedom 3). By doing this you
can give the whole community a chance to benefit from your changes.
Free = 不要錢 !?
Free = You don't have to pay for it !?
The Free Software DefinitionThe Free Software Definition
■ The freedom to run the program, for any purpose
(freedom 0).
■ The freedom to study how the program works, and
change it to make it do what you wish (freedom 1).
■ The freedom to redistribute copies so you can help your
neighbor (freedom 2).
■ The freedom to distribute copies of your modified
versions to others (freedom 3). By doing this you
can give the whole community a chance to benefit from your changes.
Free = 不要錢 !?
Free = You don't have to pay for it !?
The Free Software DefinitionThe Free Software Definition
■ The freedom to run the program, for any purpose
(freedom 0).
■ The freedom to study how the program works, and
change it to make it do what you wish (freedom 1).
■ The freedom to redistribute copies so you can help your
neighbor (freedom 2).
■ The freedom to distribute copies of your modified
versions to others (freedom 3). By doing this you
can give the whole community a chance to benefit from your changes.
Free = 不要錢 !?
Free = You don't have to pay for it !?
免費女神 !?
Statue of Gratis!?
The Free Software DefinitionThe Free Software Definition
■ The freedom to run the program, for any purpose
(freedom 0).
■ The freedom to study how the program works, and
change it to make it do what you wish (freedom 1).
■ The freedom to redistribute copies so you can help your
neighbor (freedom 2).
■ The freedom to distribute copies of your modified
versions to others (freedom 3). By doing this you
can give the whole community a chance to benefit from your changes.
Free = 不要錢 !?
當然不是 !Defnitely NOT!
The Free Software DefinitionThe Free Software Definition
■ The freedom to run the program, for any purpose
(freedom 0).
■ The freedom to study how the program works, and
change it to make it do what you wish (freedom 1).
■ The freedom to redistribute copies so you can help your
neighbor (freedom 2).
■ The freedom to distribute copies of your modified
versions to others (freedom 3). By doing this you
can give the whole community a chance to benefit from your changes.
This picture is downloaded here: http://cs.stanford.edu/people/eroberts/cs181/projects/open-source/bruce.jpg
Just for fair use in this slide and not granted any license to any other use.
Open Source SoftwareOpen Source Software
■ Open Source Software■ Bruce Perens & Eric Steven Raymond■ Open Source Initiative (OSI) 1998-
開放源碼促進會
Open Source SoftwareOpen Source Software
■ Open Source Software■ Bruce Perens & Eric Steven Raymond■ Open Source Initiative (OSI) 1998-■ Eclecticism: commercial thinking
Open Source SoftwareOpen Source Software
■ Open Source Software■ Bruce Perens & Eric Steven Raymond■ Open Source Initiative (OSI) 1998-■ Eclecticism: commercial thinking■ The Cathedral and the Bazaar
These slides are licensed under creative commons - attribution - share alike 3.0 unported.
Hong Kong Open Source Conference 2014香港開源年會 2014/3/29 Sat.
The Rules of Open Source and Collaboration:Copyright and Public License
■ The Default Rule of Copyright and the goal of Free/ Open Source Software
■ The Legal Framework to Protect Open Source and Collaboration: Public License and Copyleft
■ Conclusion
LicenseLicense
■ License– 許可證– 授權(授權條款)
■ The rule is from property law■ You can use my property, only if...
– The conditions are met.
■ FOSS License■ Prerequisites: the licensor has the right
(copyright) to license.
Public LicensePublic License
■ Advantage:■ You can just use open source code without
gaining permission as long as all the conditions of the license are met.– The problem of “Nail House ( 釘子戶 )” of a
collaborative work by many contributors– Use = Agree the Terms– Free to join, Free to fork.
Public LicensePublic License
■ Legal cost:■ If you don't comply the license, it happens two
legal cost: – Not only breach of the contract ( 違約 ),– But also infringement ( 侵權 ).
■ If someone violates the license, the licensor can use the weapon offered by copyright law:– Demages 損害賠償– Injunction 假處分 / 禁制令(商品下架)– Criminal liability 刑事責任
The mechanism of open source: CopyleftThe mechanism of open source: Copyleft
■ Copyleft 著佐權■ Characteristic:
■ To ensure the four freedoms■ Based on copyright law■ Pre-license to the public■ One who makes
modifications must licensethe derivative work withthe same license.
授權拘束性License Inheritance
GPL
Proprietary Software License
LGPL
AGPLEPL/CPL
MIT/BSD
Apache2.0
MPL/CDDL
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
GPL
Proprietary Software License
LGPL
AGPLEPL/CPL
MIT/BSD
Apache2.0
MPL/CDDL
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Copyleft Non-Copyleft
GPL
Proprietary Software License
LGPL
AGPLEPL/CPL
MIT/BSD
Apache2.0
MPL/CDDL
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Non-CopyleftStrong Copyleft Weak Copyleft
GPL
Proprietary Software License
AGPL
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Strong Copyleft
GPL
Proprietary Software License
AGPL
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Strong Copyleft
GeneralPublic
License
DerivativeWork
must licenseunder GPL
LinkModifyMerge
GPL
Proprietary Software License
AGPL
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Strong Copyleft
GeneralPublic
License
DerivativeWork
must licenseunder GPL
LinkModifyMerge
Exp.Seperate &
Independent
GPL
Proprietary Software License
AGPL
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Strong Copyleft
GeneralPublic
License
DerivativeWork
must licenseunder GPL
LinkModifyMerge
Exp.Seperate &
IndependentI open to you,you also have
to open to others我佛心對你
你也要佛心對人
GPL
Proprietary Software License
AGPL
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Strong Copyleft
GeneralPublic
License
DerivativeWork
must licenseunder GPL
LinkModifyMerge
Exp.Seperate &
IndependentI open to you,you also have
to open to others我佛心對你
你也要佛心對人
Take it orleave it.
不爽不要用
How to trigger the obligation of Copyleft?How to trigger the obligation of Copyleft?
Alice
binary &source code
GPLedProgram A
DerivativeProgram B
Bob
How to trigger the obligation of Copyleft?How to trigger the obligation of Copyleft?
Alice
binary &source code
GPLedProgram A
DerivativeProgram B
Bob
B can be closed.Even if you know thatB exists, you don't
have any right to ask Bto open source.
How to trigger the obligation of Copyleft?How to trigger the obligation of Copyleft?
Alice
binary &source code
GPLedProgram A
DerivativeProgram B
Bob
distributebinarycode
Charlie
How to trigger the obligation of Copyleft?How to trigger the obligation of Copyleft?
Alice
binary &source code
GPLedProgram A
DerivativeProgram B
Bob
distributebinarycode
Charlie
I want tomodify it.
Give methe source
code
How to trigger the obligation of Copyleft?How to trigger the obligation of Copyleft?
Alice
binary &source code
GPLedProgram A
DerivativeProgram B
Bob
distributebinarycode
Charlie
I want tomodify it.
Give methe source
code
Bobmustopen
source
How to trigger the obligation of Copyleft?How to trigger the obligation of Copyleft?
Alice
binary &source code
GPLedProgram A
DerivativeProgram B
Bob
distributebinarycode
Charlie
I want tomodify it.
Give methe source
code
Bobmustopen
source
The act triggers the obligation of
Copyleft
GPL
Proprietary Software License
AGPL
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Strong Copyleft
AfferoGPL
(AGPL)
Net-basedCopyleft
Use
Modify
GPL
Proprietary Software License
AGPL
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Strong Copyleft
AfferoGPL
(AGPL)
Net-basedCopyleft
Use
If you just useAGPL program,you don't have
to release underAGPL
GPL
Proprietary Software License
AGPL
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Strong Copyleft
AfferoGPL
(AGPL)
Net-basedCopyleft
Modify
If you modify the project or
mergethe code to your own project,
you have torelease yourproject under
AGPL.
GPL
Proprietary Software License
AGPL
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Strong Copyleft
AfferoGPL
(AGPL)
Net-basedCopyleft
Use
Modify
The mechanism of open source: CopyleftThe mechanism of open source: Copyleft
■ The obligation to open source:
■ The derivative work will keep the same license and conditions, so the freedom wouldn't be taken.
■ The derivative of derivative works...The open source code will be more and more.
■ The copyright holder will have stronger bargaining power to “uncooperative people” and hasstanding to ask them to open source.
The mechanism of open source: CopyleftThe mechanism of open source: Copyleft
■ The obligation to open source:
■ Companies may not like it because
– Their copyright will be forced to open– They see the code as their trade secret and
commercial advantage■ But they'll be sue if not comply with the rule.
■ Another problem is license compatibility.
■ Many copyleft licenses are notcompatible with each other.
– Ex: GPL-2.0 / GPL-3.0
Proprietary Software License
LGPL
EPL/CPL
MPL/CDDL
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Weak Copyleft
Proprietary Software License
LGPL
EPL/CPL
MPL/CDDL
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Weak CopyleftLibraryLesser
Copyleftis lesser
Proprietary Software License
LGPL
EPL/CPL
MPL/CDDL
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Weak CopyleftLibraryLesser
Copyleftis lesser
Use
Modify
Proprietary Software License
LGPL
EPL/CPL
MPL/CDDL
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Weak CopyleftLibraryLesser
Copyleftis lesser
Use
Dynamic link:You don't have to
release yourprogram under
LGPL.
Proprietary Software License
LGPL
EPL/CPL
MPL/CDDL
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Weak CopyleftLibraryLesser
Copyleftis lesser
Modify
If you modify the lib or
merge the lib to your own projectwith statics link,
you have torelease yourproject under
LGPL.
Weak CopyleftWeak Copyleft
■ File based copyleft■ MPL: Mozilla Public License■ CDDL: Common Development and Distribution
License■ Module based copyleft
■ EPL: Eclipse Public License■ CPL: Common Public License
MPLMPL
MPL X
Y YYX
X
Y
X
Y
MPL
MPLX LicenseY License
Compatible with each other.
MPL Program
Proprietary Software License
MIT/BSD
Apache2.0
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Non-Copyleft
Proprietary Software License
MIT/BSD
Apache2.0
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Non-CopyleftMITBSD
Apache
Copyrightnotice
Disclaimer
Example of BSD licenseExample of BSD license
Example of BSD licenseExample of BSD license
Copyright Notice
Example of BSD licenseExample of BSD license
Copyright Notice
Example of BSD licenseExample of BSD license
License Content
Example of BSD licenseExample of BSD license
License Content
Example of BSD licenseExample of BSD license
Disclaimer
Example of BSD licenseExample of BSD license
免責聲明Disclaimer
Example of BSD licenseExample of BSD license
著作權聲明Copyright Notice
免責聲明Disclaimer
授權範圍
Proprietary Software License
MIT/BSD
Apache2.0
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Non-CopyleftMITBSD
Apache
Copyrightnotice
Disclaimer
GPL
Proprietary Software License
LGPL
AGPLEPL/CPL
MIT/BSD
Apache2.0
MPL/CDDL
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Copyleft Non-Copyleft
GPL
Proprietary Software License
LGPL
AGPLEPL/CPL
MIT/BSD
Apache2.0
MPL/CDDL
Spectrum of Freedom & RestrictionSpectrum of Freedom & Restriction
Public Domain
Non-CopyleftStrong Copyleft Weak Copyleft
How to choose license?How to choose license?
■ To the original copyright holder■ Choose any license you want
– Strong/ weak/ non copyleft– Compatibility with relative open source project– Business model, ex: dual-license
How to choose license?How to choose license?
■ To derivative software holder■ You take the code from copyleft project
– GPL● all your code in the same project
– LGPL● It depends on whether you use dynamic link or statics link to the library,
or directly develop your lib base on the LGPL lib.
– MPL/ EPL● If you use the files/ modules from MPL/ EPL project to create new files/
modules, then you should open them; if you don't use any code from the original files/ modules, then you have the whole copyright of your patch.
■ You take the code from non-copyleft project– You just need to meet the only two conditions (copyright notice
and disclaimer), you can do any thing you want, including using any other open source licenses or even commercial license to release your code (or not release).
These slides are licensed under creative commons - attribution - share alike 3.0 unported.
Hong Kong Open Source Conference 2014香港開源年會 2014/3/29 Sat.
The Rules of Open Source and Collaboration:Copyright and Public License
■ The Default Rule of Copyright and the goal of Free/ Open Source Software
■ The Legal Framework to Protect Open Source and Collaboration: Public License and Copyleft
■ Conclusion
Cases of GPL violationCases of GPL violation
■ To open or not to open, that is NOT a question...■ Until the companies lose the cases...
Harald Welte v. D-link
BusyBox v. 14 companies
2006
2009
Harald Welte v. D-link
BusyBox v. 14 companies
2006
2009
Welte v. D-Link (2006)Welte v. D-Link (2006)
German Branch
msdosfs, initrd, mtd1. A part of Linux kernel2. Copyright holders:
Werner Almesberger (Austria)David Woodhouse (UK)Harald Welte (Germany)
Use source code
Welte v. D-Link (2006)Welte v. D-Link (2006)
Harald Welte
Ask
msdosfs, initrd, mtd1. A part of Linux kernel2. Copyright holders:
Werner Almesberger (Austria)David Woodhouse (UK)Harald Welte (Germany)
German Branch
RepresentativeAuthorization
Use source code
Welte v. D-Link (2006)Welte v. D-Link (2006)
Harald Welte
Ask
msdosfs, initrd, mtd1. A part of Linux kernel2. Copyright holders:
Werner Almesberger (Austria)David Woodhouse (UK)Harald Welte (Germany)
German Branch???I don't know what you're saying...
RepresentativeAuthorization
Use source code
Welte v. D-Link (2006)Welte v. D-Link (2006)
Harald Welte
RepresentativeAuthorization
msdosfs, initrd, mtd1. A part of Linux kernel2. Copyright holders:
Werner Almesberger (Austria)David Woodhouse (UK)Harald Welte (Germany)
German Branch
FrankfurtDistrict Court
Sue
Infringement
Use source code
Welte v. D-Link (2006)Welte v. D-Link (2006)
Harald Welte
RepresentativeAuthorization
msdosfs, initrd, mtd1. A part of Linux kernel2. Copyright holders:
Werner Almesberger (Austria)David Woodhouse (UK)Harald Welte (Germany)
German Branch
FrankfurtDistrict Court
Sue
Infringement
Allcustomers
Use source code
1. open source codes
2. GPL notifcation
damages
BusyBox v. 14 companies 2009
Busybox v. 14 companies (2009)Busybox v. 14 companies (2009)
Defenders are 14companies
Busybox combines tiny versions of many common UNIX utilities into a single small executable.
Licensed under GPL-2.0.
Copyright holder:● Erik Anderson (US)● Other developers
Use source code
Best Buy, Samsung, We s t i n g h o u s e ,
JVC, WD, Robert Bosch, Phoebe Mircro, Humanx,
Comtrend ( 康全科技 ) , Dobbs-Standford, Versa,
Zyxel ( 合勤科技 ) , Astak, GCI
Busybox v. 14 companies (2009)Busybox v. 14 companies (2009)
Defenders are 14companies
Busybox combines tiny versions of many common UNIX utilities into a single small executable.
Licensed under GPL-2.0.
Copyright holder:● Erik Anderson (US)● Other developers
Use source code
Busybox v. 14 companies (2009)Busybox v. 14 companies (2009)
Defenders are 14companies
Busybox combines tiny versions of many common UNIX utilities into a single small executable.
Licensed under GPL-2.0.
Copyright holder:● Erik Anderson (US)● Other developers
Use source code
United StatesDistrict ofNew York
Sue
Erik AndersonFree Software Conservancy
Busybox v. 14 companies (2009)Busybox v. 14 companies (2009)
Defenders are 14companies
Busybox combines tiny versions of many common UNIX utilities into a single small executable.
Licensed under GPL-2.0.
Copyright holder:● Erik Anderson (US)● Other developers
Use source code
Erik AndersonFree Software Conservancy
United StatesDistrict ofNew York
Sue
1. Many upstream OEMs/ODMs Manufacturers are Taiwan Companies.2. 13 companies settled out of courtor are working with FSC.3. The court is ordering Westinghouse topay $90,000 in damages and to give theHDTVs that include the BusyBox code to the Conservancy.
Industry AdoptionIndustry Adoption
■ To open or not to open, that is NOT a question...■ Until the companies lose the cases...
Harald Welte v. D-link
BusyBox v. 14 companies
2006
2009
These slides are licensed under creative commons - attribution - share alike 3.0 unported.
Hong Kong Open Source Conference 2014香港開源年會 2014/3/29 Sat.
The Rules of Open Source and Collaboration:Copyright and Public License
■ The Default Rule of Copyright and the goal of Free/ Open Source Software
■ The Legal Framework to Protect Open Source and Collaboration: Public License and Copyleft
■ Conclusion
Free Material besides codeFree Material besides code