The Shared Source Initiative (SSI) is a source-available software licensing scheme launched by Microsoft in May 2001. 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. Overview 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 and are regarded by the Free Software Foundation as free software licenses. 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. Microsoft also uses specific licenses for some of their products, such as the Shared Source CLI License and the Microsoft Windows Embedded CE 6.0 Shared Source License. Free and open-source licenses The following licenses are considered open-source by the Open Source Initiative and free by the Free Software Foundation. Microsoft Public License (Ms-PL) 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. Initially titled Microsoft Permissive License, it was renamed to Microsoft Public License while being reviewed for approval by the Open Source Initiative (OSI). The license was approved on October 12, 2007, along with the Ms-RL. According to the Free Software Foundation, it is a free software license but not compatible with the GNU GPL. Ms-PL provides a free and flexible licensing for developers using source codes under this license. However, the Ms-PL is a copyleft license because it requires the source code of software it governs to be distributed only under the same license (the Ms-PL). Microsoft Reciprocal License (Ms-RL) This Microsoft license allows for distribution of derived code so long as the modified source files are included and retain the Ms-RL. The Ms-RL allows those files in the distribution that do not contain