ECMA is mentioning the following in its answer of February 2007:
Pursuant to such Patent Declaration Form, Microsoft has provided assurances to ITTF that any such essential claims vis-à-vis DIS 29500 will be available for full or partial implementations under three different approaches (from which an implementer can select). These options include Microsoft’s Open Specification Promise (see http://www.microsoft.com/interop/osp/default.mspx), Microsoft’s Covenant http://office.microsoft.com/en-us/products/HA102134631033.aspx) and a royalty-free Reasonable And Non-Discriminatory (RAND) license.
Furthermore, a Microsoft employee mentioned here:
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.
Where is is possible to get a copy of this licence?