Source-available software

Shared source is a family of Microsoft software licenses, each with varying restrictions. Depending on the license, the license restrictions could range from the most restrictive such that it could be only be viewed and to the least restrictive that it could be viewed, modified, or redistributed the source code for either commercial or non-commercial purposes. These are not the default licenses on Microsoft products, they must be acquired separately only by eligible customers, in a limited number of countries.

Benefits of shared source

Shared source licenses provide a number of benefits to end users that are not present in other proprietary software licenses. Primary among these is the availability of source code for reference when developing complementary systems. For example, having the source code to significant portions of an operating system aids application developers in maintaining stability and consistency in their own programs. The availability of source code also permits review and auditing from a security perspective, something which many large corporations and governments are now mandating.

Shared source benefits the copyright holder in that much tighter control is kept over the use of their product than open source licenses, which generally include the voluntary abdication of many of the author's rights. From the perspective of companies which are used to developing proprietary software, this is a smaller transition to make, and may be seen as an interim step to full open source disclosure.

Comparison of Open Source and Shared Source

From an end-user and original author perspective, shared source licenses share many of the benefits (and drawbacks) of open source licenses. From a "downstream" developer's standpoint, some of the shared source licenses stop short of the rights granted by an open source license while some of the shared source licenses, such as the Microsoft Permissive License and Microsoft Community License, could be characterized as open source licenses.

	Shared Source	Open Source
Availability	Restricted to customers or partners in a limited number of countries who meet the criteria	Available to anyone in any country and of any economic status
Benefits to downstream developers	easier integration	easier integration
Upstream benefits	Select partners may contribute source code to programs approved by Microsoft.	Anyone may submit code for review to the development community of any program.

Notable shared source programs

Microsoft Enterprise Source Licensing

Microsoft gives enterprise customers viewing access to some parts of some versions of the Microsoft Windows operating systems. This is among the most restrictive of the Shared Source licenses, allowing no modifications of the code or verification that the code shown is actually the code used.

Microsoft Windows Academic Licensing

This program makes some Windows kernel technologies and code available to universities for teaching purposes. The program also includes curriculum resources and projects.

Microsoft Shared Source Common Language Infrastructure

The first widely-distributed shared source license program is Shared Source CLI, the shared source implementation of the Common Language Infrastructure. The licensing permits non-commercial modification and distribution of the source code, as long as all distributions include the original license, or one encompassing the original terms .

Microsoft Shared Source Common Language Infrastructure is neither free software according to the Free Software Foundation [1], nor OSI-approved open source.

Microsoft Community License (Ms-CL)

This is the least restrictive of the Microsoft licenses and allows for distribution of derived code so long as the modified files retain the royalty-free, non-exclusive copyright and patent grants of the original license.

On December 9 2005, blogger and programmer John Cowan submitted this license to the Open Source Initiative for approval. [2] [3] It has not been accepted.

Criticism

Free software enthusiasts see shared source licenses as being equal to proprietary licenses. Free software pioneer Richard Stallman has said that Shared Source is "just another name for a nondisclosure agreement". Prominent open source figure Bruce Perens has described its policies as "look but don't touch—and we control everything". [4]. Two of the Shared Source licenses were interpreted as free software licenses by FSF Europe, but Microsoft has not used either of these two licences for any large projects. However, the distribution of many licenses is considered an attempt to obfuscate the meaning of "Shared Source" and generate support from the free software community. [5]

See also

• Free Software
• Glossary of legal terms in technology
• Open Source

External links

• Microsoft Shared Source Initiative Home Page
• Microsoft Shared Source Basics
• List of Microsoft Shared Source Licensing Programs
• Video interview with Jon Rosenberg, Director of Shared Source Programs at Microsoft
• "Opening Windows, Just a Little". Wired News. Retrieved August 31. {{cite web}}: Check date values in: |accessdate= (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
• "Stallman takes Gates to task over GPL". ZDNet. Retrieved October 17. {{cite web}}: Check date values in: |accessdate= (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
• "On 'Shared-Source' by Michael Tiemann". Open Source Initiative. Retrieved October 17. {{cite web}}: Check date values in: |accessdate= (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
• GNU's List of Non-Free Licenses