Source-available software

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A source-available software source code distribution model, also called a shared source model, includes arrangements where the source can be viewed, and in some cases modified, but without necessarily meeting the criteria to be called open source.[1] The licenses associated with the offerings range from allowing code to be viewed for reference, to allowing code to be modified and redistributed for both commercial and non-commercial purposes.[citation needed]


The term shared source was coined as part of Microsoft's Shared Source Initiative, which was launched in May 2001.[2] The program includes a spectrum of technologies and licenses, and most of its source code offerings are available for download after eligibility criteria are met.

Microsoft's Shared Source Initiative allows individuals and organizations to access Microsoft's source code for reference (e.g. when developing complementary systems), for review and auditing from a security perspective (mostly wanted by some large corporations and governments), and for development (academic institutions, OEMs, individual developers).

As part of the framework, Microsoft released 5 licenses for general use. Two of them, Microsoft Public License and Microsoft Reciprocal License, have been approved by the Open Source Initiative as open source licenses[3][4] and are regarded by the Free Software Foundation as free software licenses.[5] Other shared source licenses are proprietary, and thus allow the copyright holder to retain tighter control over the use of their product.

Microsoft's Shared Source Initiative has been imitated by other companies such as RISC OS Open Ltd.[6]

Microsoft also uses specific licenses for some of their products, for example the Shared Source CLI License[7] and the Microsoft Windows Embedded CE 6.0 Shared Source License.[8]

Distinction from free software and open-source software[edit]

Any software is source available software as long its source code is distributed along with it, even if the user has no legal rights to use, share, modify or even compile it. It is possible for a software to be both source available software and proprietary software, usually because the publisher, developers or another person retains copyright on the software.[citation needed]

In contrast, the definitions of free software and open-source software are much narrower. Free software and/or open-source software is also always source available software, but not all source available software is also free software and/or open-source software. This is because the official definitions of those terms require the software to have their source code available in some form.[citation needed]


Two specific shared source licenses are interpreted as free software and open source licenses by FSF and OSI. However, former OSI president Michael Tiemann considers the phrase "Shared Source" itself to be a marketing term created by Microsoft. He argues that it is "an insurgent term that distracts and dilutes the Open Source message by using similar-sounding terms and offering similar-sounding promises".[9]

Free and open-source licenses[edit]

The following licenses are considered open-source by the Open Source Initiative and free by the Free Software Foundation.

Microsoft Public License (Ms-PL)[edit]

This is the least restrictive of the Microsoft licenses and allows for distribution of compiled code for either commercial or non-commercial purposes under any license that complies with the Ms-PL. Redistribution of the source code itself is permitted only under the Ms-PL.[10] Initially titled Microsoft Permissive License, it was renamed to Microsoft Public License while being reviewed for approval by the Open Source Initiative (OSI).[11] The license was approved on October 12, 2007, along with the Ms-RL.[12] According to the Free Software Foundation, it is a free software license but not compatible with the GNU GPL.[5]

Microsoft Reciprocal License (Ms-RL)[edit]

This Microsoft license allows for distribution of derived code so long as the modified source files are included and retain the Ms-RL.[13] The Ms-RL allows those files in the distribution that do not contain code originally licensed under Ms-RL to be licensed according to the copyright holder's choosing. This is similar, but not the same as the CDDL, EPL or LGPL (GPL with a typical "linking exception").[citation needed] Initially known as the Microsoft Community License, it was renamed during the OSI approval process.

On December 9, 2005, the Ms-RL license was submitted to the Open Source Initiative for approval by John Cowan.[14] OSI then contacted Microsoft and asked if they wanted OSI to proceed. Microsoft replied that they did not wish to be reactive and that they needed time to review such a decision.[15]

At the O'Reilly Open Source Convention in July 2007, Bill Hilf, director of Microsoft's work with open source projects, announced that Microsoft had formally submitted Ms-PL and Ms-RL to OSI for approval.[16] It was approved on October 12, 2007, along with the Ms-PL.[12] According to the Free Software Foundation, it is a free software license but not compatible with the GNU GPL.[5]

Restricted licenses[edit]

The following licenses have limitations that prevent them from being open-source according to the Open Source Initiative and free to the Free Software Foundation.

GitLab Enterprise Edition License (EE License)[edit]

The GitLab Enterprise Edition License is used exclusively by GitLab's commercial offering.[17] GitLab also releases a Community Edition under the MIT License.[18]

GitLab Inc. openly discloses that the EE License makes their Enterprise Edition product "proprietary, closed source code."[19] However, the company makes the source code of the Enterprise Edition public, as well as the repository's issue tracker, and allows users to modify the source code.[20] The dual release of the closed-source Enterprise Edition and the open-source Community Edition makes GitLab an open core company.

Microsoft Limited Public License (Ms-LPL)[edit]

This is a version of the Microsoft Public License in which rights are only granted to developers of Microsoft Windows-based software.[21] This license is not open source, as defined by the OSI, because the restriction limiting use of the software to Windows violates the stipulation that open-source licenses must be technology-neutral.[22] It is also considered to be non-free by the Free Software Foundation due to this restriction.[5]

Microsoft Limited Reciprocal License (Ms-LRL)[edit]

This is a version of the Microsoft Reciprocal License in which rights are only granted when developing software for a Microsoft Windows platform.[23] Like the Ms-LPL, this license is not open source because it is not technology-neutral[22] due to its restriction that licensed software must be used on Windows, and is also not considered free by the Free Software Foundation due to this restriction.[5]

Microsoft Reference Source License (Ms-RSL)[edit]

This is the most restrictive of the Microsoft Shared Source licenses. The source code is made available to view for reference purposes only, mainly to be able to view Microsoft classes source code while debugging.[24] Developers may not distribute or modify the code for commercial or non-commercial purposes.[25] The license has previously been abbreviated Ms-RL, but Ms-RL now refers to the Microsoft Reciprocal License.[13]

Scilab License[edit]

Prior to version 5, Scilab described itself as "the open source platform for numerical computation"[26] but had a license[27] that forbade commercial redistribution of modified versions.

SugarCRM Public License[edit]

In 2007 Michael Tiemann, president of OSI, had criticized[28] companies such as SugarCRM for promoting their software as "open source" when in fact it did not have an OSI-approved license. In SugarCRM's case, it was because the software is so-called "badgeware"[29] since it specified a "badge" that must be displayed in the user interface (SugarCRM has since switched to GPLv3[30]).

TrueCrypt License[edit]

The TrueCrypt License was used by the TrueCrypt disk encryption utility.[31] When TrueCrypt was discontinued, the VeraCrypt fork switched to the Apache License, but retained the TrueCrypt License for code inherited from TrueCrypt.[32]

The Open Source Initiative rejects the TrueCrypt License, as "it has elements incompatible with the OSD."[33] The Free Software Foundation criticizes the license for restricting who can execute the program, and for enforcing a trademark condition.[5]

See also[edit]


  1. ^ "DoD Open Source Software (OSS) FAQ". Chief Information Officer. U.S. Department of Defense. Retrieved 23 Jul 2018. 
  2. ^ Geekzone: Microsoft announces expansion of Shared Source Initiative
  3. ^ Ms-PL
  4. ^ Ms-RL
  5. ^ a b c d e f "Various Licenses and Comments about Them". GNU Operating System. Free Software Foundation. Retrieved 23 Jul 2018. 
  6. ^ RISC OS Open
  7. ^ "Shared Source Common Language Infrastructure License". 
  8. ^ Microsoft Windows Embedded CE 6.0 Shared Source License Terms (“License”)
  9. ^ Michael Tiemann (2007-11-11). "Who Is Behind "Shared Source" Misinformation Campaign?". Retrieved 2011-03-12. Shared source is a marketing term created and controlled by Microsoft. Shared source is not open source by another name. Shared source is an insurgent term that distracts and dilutes the Open Source message by using similar-sounding terms and offering similar-sounding promises. And to date, 'shared source' has been a marketing dud as far as Open Source is concerned. 
  10. ^ "Microsoft Public License (Ms-PL)". 
  11. ^ Foley, Mary. "Microsoft gets the open-source licensing nod from the OSI". ZDNet. Retrieved 22 May 2015. 
  12. ^ a b "OSI Approves Microsoft License Submissions". 2007-10-17. Retrieved 2013-08-08. Acting on the advice of the License Approval Chair, the OSI Board today approved the Microsoft Public License (Ms-PL) and the Microsoft Reciprocal License (Ms-RL). The decision to approve was informed by the overwhelming (though not unanimous) consensus from the open source community that these licenses satisfied the 10 criteria of the Open Source definition, and should therefore be approved. 
  13. ^ a b "Microsoft Reciprocal License (Ms-RL)". 
  14. ^ John Cowan (2005-12-09). "For Approval: Microsoft Community License". license-discuss mailing list. 
  15. ^ Peter Galli (2006-08-22). "Blogger Can't Tempt Microsoft To Drink OSI Kool-Aid". eWeek. 
  16. ^ Tim O'Reilly (2007-07-26). "Microsoft to Submit Shared Source Licenses to OSI". O'Reilly Radar. 
  17. ^ "The GitLab Enterprise Edition (EE) license (the "EE License")". GitLab. GitLab Inc. 16 May 2018. Retrieved 23 Jul 2018. 
  18. ^ "GitLab Community Edition LICENSE file". GitLab. GitLab Inc. 15 May 2018. Retrieved 23 Jul 2018. 
  19. ^ Sijbrandij, Sid (20 Jul 2016). "GitLab is open core, GitHub is closed source". GitLab. GitLab Inc. Retrieved 23 Jul 2018. 
  20. ^ "GitLab Community Edition". GitLab Inc. Retrieved 23 Jul 2018. 
  21. ^ "Microsoft Limited Public License (Ms-LPL)". 
  22. ^ a b "The Open Source Definition". Open Source Initiative. 
  23. ^ "Microsoft Limited Reciprocal License (Ms-LRL)". 
  24. ^ "Microsoft Reference Source License". Microsoft. 2016-07-06. Retrieved 2016-07-06. "Reference use" means use of the software within your company as a reference, in read only form, for the sole purposes of debugging your products, maintaining your products, or enhancing the interoperability of your products with the software, and specifically excludes the right to distribute the software outside of your company. 
  25. ^ "Microsoft Reference Source License". 
  26. ^ "The open source platform for numerical computation". INRIA. Retrieved 2008-01-04. 
  27. ^ "SCILAB License". INRIA. Archived from the original on 2005-12-12. Retrieved 2008-01-04. 
  28. ^ Tiemann, Michael (2007-06-21). "Will The Real Open Source CRM Please Stand Up?". Open Source Initiative. Retrieved 2008-01-04. 
  29. ^ Berlind, David (21 November 2006). "Are SugarCRM, Socialtext, Zimbra, Scalix and others abusing the term "open source?"". ZDNet. Archived from the original on 1 January 2008. Retrieved 4 January 2008. 
  30. ^ Vance, Ashlee (2007-07-25). "SugarCRM trades badgeware for GPL 3". The Register. Retrieved 2008-09-08. 
  31. ^ "truecrypt-archive/License-v3.1.txt at master · DrWhax/truecrypt-archive". GitHub. 28 Mar 2014. Retrieved 23 Jul 2018. 
  32. ^ "root/License.txt". VeraCrypt. TrueCrypt Foundation. 17 Oct 2016. Retrieved 23 Jul 2018. 
  33. ^ Phipps, Simon (15 November 2013), TrueCrypt or false? Would-be open source project must clean up its act, InfoWorld, retrieved 20 May 2014 

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