The board of the Open Source Initiative (OSI) has approved two Microsoft licenses that allow proprietary source code to be shared, a move that is likely to inspire protest and spur controversy for die-hard open-source proponents.

The Microsoft Public License (MPL) and the Microsoft Reciprocal License (MRL), two of Microsoft's so-called "shared source" licenses, are now viable OSI licenses for distributing open-source code alongside more widely used community licenses such as the GNU General Public License and the Mozilla Public License.

"Today's approval by the OSI concludes a tremendous learning experience for Microsoft and I look forward to our continued participation in the open-source community," said Microsoft General Manager of Windows Server Marketing and Platform Strategy Bill Hilf.

Microsoft submitted licenses from its Shared Source Initiative to the OSI in July, an announcement made at the O'Reilly Open Source Convention. The news was generally well received by top open-source community leaders at the time, though some noted that a move from Microsoft to work with the community on open-source licenses could have come a lot sooner.

The MPL and MRL are two of three licenses that Microsoft offers in its Shared Source Initiative, which it has offered for about five years as a way to share source code without having to work with open-source organizations or companies. The other is the Microsoft Reference License, which is the most restrictive of the three and was not submitted for approval.

The MPL is the least restrictive of the Shared Source licenses, allowing licensees to view, modify and redistribute the source code for either commercial or non-commercial purposes. The license also allows licensees to alter the source code they share with others as well as to charge a licensing fee for their work if they choose. The MRL, which the company recommends for collaborative development projects, carries specific requirements if licensees combine their original code with MRL-licensed code. It does, however, allow for non-commercial and commercial modification and redistribution of licensed software.

Red Hat executive Michael Tiemann, who also serves as president of the OSI, said that while some in the community balked at the OSI accepting licenses from a company that historically has not been open-source friendly, in the end, the licenses spoke for themselves. "They do have two licenses that went through the community process and did sustain the open-source definition," he said.