Office Open XML - Licensing

Licensing

Under the Ecma International code of conduct in patent matters, participating and approving member organisations of ECMA are required to make available their patent rights on a reasonable and non-discriminatory (RAND) basis.

Holders of patents which concern ISO/IEC International Standards may agree to a standardized license governing the terms under which such patents may be licensed, in accord with the ISO/IEC/ITU common patent policy.

Microsoft, the main contributor to the standard, provided a Covenant Not to Sue for its patent licensing. The covenant received a mixed reception, with some like the Groklaw blog criticizing it, and others such as Lawrence Rosen, (an attorney and lecturer at Stanford Law School), endorsing it.

Microsoft has added the format to their Open Specification Promise in which

Microsoft irrevocably promises not to assert any Microsoft Necessary Claims against you for making, using, selling, offering for sale, importing or distributing any implementation to the extent it conforms to a Covered Specification

This is limited to applications which do not deviate from the ISO/IEC 29500:2008 or Ecma-376 standard and to parties that do not "file, maintain or voluntarily participate in a patent infringement lawsuit against a Microsoft implementation of such Covered Specification". The Open Specification Promise was included in documents submitted to ISO/IEC in support of the ECMA-376 fast track submission. Ecma International asserted that, "The OSP enables both open source and commercial software to implement ".