The Open Source Initiative (OSI) has approved the Microsoft Public Licence and Microsoft Reciprocal Licence, officially branding them as open source licences.

The OSI approves licences by validating compliance to 10 rules set in the Open Source Definition.

The decision was reached with an "overwhelming majority" of the votes, but not unanimously, OSI president Michael Tiemann said in a posting on the group's website.

Microsoft welcomed the decision. "This is a significant milestone in the progression of Microsoft's open source strategy and the company's ongoing commitment to participation in the open source community to effectively meet the evolving needs of developers," the company said in an emailed statement.

Microsoft's submission had sparked debate within the open source community over the software firm's intentions.

Critics charged that the addition of the licence was an attempt by Microsoft to undermine open source. The company has repeatedly accused open source vendors of violating its patents.

Chris DiBona, open source programme manager at Google, had argued that Microsoft should be required to meet requirements beyond the 10 listed in the Open Source Definition to gain approval for its licences.

DiBona's plea, however, was turned down. Tiemann said in his posting that the OSI and Microsoft enjoyed a constructive dialogue "in spite of recent negative interactions between Microsoft and the open source community".