The Open Source Initiative (OSI) has approved two Microsoft "shared source" licences.
The OSI has approved the Microsoft Public License (Ms-PL) and the Microsoft Reciprocal License (Ms-RL).
The OSI said the licences satisfy the ten open-source criteria set by of the Open Source definition.
Microsoft's "shared source" initiative was launched around five years ago, and allows it to contribute to the open source community without having to closely interact with other firms and developers.
The OSI acknowledged there was some opposition in the open source community to the Microsoft licences being approved.
The OSI said, "Microsoft did not ask for special treatment, and did not receive any. In spite of recent negative interactions between Microsoft and the open source community, the spirit of the dialogue was constructive, and we hope that carries forward to a constructive outcome as well."