The Software Freedom Law Center has published an analysis of the Open Specification Promise (OSP), concluding that "the OSP doesn't permit free software implementation: it permits implementation under free software licenses so long as the resulting code isn't used freely".
The OSP is designed to remove freedoms for GPL developers, such as sub-licensing.
Here is the conclusion of the SFLC:
As the final period for consideration of OOXML by ISO elapses, SFLC recommends against the establishment of OOXML as an international standard and cautions GPL implementers not to rely on the OSP.
It's time to call Microsoft Licensing for getting a copy of their RAND license:
Some companies (sometimes that have a large commercial operation) prefer to enter into a bi-lateral license agreement as opposed to relying on a CNS or OSP-like promise.
The person who manages to get a copy of the RAND license terms will get an icecream.