The License for the Microsoft Office Open XML document formats is attached below for anyone interested in reading it. It's not that long.
Like the specification itself, the license contains a seIf-contradiction: it is a promise that is not, in practise, a promise.
In short, Microsoft promises not to sue you for using the Microsoft Office Open XML formats in your software. But this promise only applies to patents Microsoft may have in the explicit parts of the Microsoft Office Open XML specification and which are described in detail there. It would not cover those parts essential to implementation which are merely referenced in the specification and lying outside the specification. See the language, "only the required portions of the...specification", emphasized below.
[The terms "Covered Specification" and "Covered Implementation" are inconveniently not defined in the License or the Open Specification Promise. Microsoft has listed all the different standards specifications that are covered by its Open Specification Promise here. These specifications listed are specifications covered by the Open Specification Promise -- each one is a "Covered Specification". For a 3rd-party who uses a covered specification and implements the work in their own software, that software is a "Covered Implementation" if it adheres to Microsoft's strict rules of what can be safely implemented...and there's the rub.]
We know of a great deal of Microsoft technology which does in fact contain patents and which lies outside the specification which would need to be implemented by such a 3rd-party for the formats to work. The Microsoft Office Open XML formats are therefore dependent upon a host of patented Microsoft technology.
In effect, this license means that if you are making a well-functioning, complete implementation of the Microsoft Office Open XML specification, then you are not covered by the "promise" in the License. In other words, Microsoft effectively prohibits you legally from making a complete and working implementation of its new formats in your software. If you do, you run the risk of being sued.
In this way, the License is stated and is to be perceived as a threat rather than a promise. In effect it says 'Stay away! Microsoft is the only entity which may implement the Microsoft Office Open XML formats!' This is a fundamental contradiction of the purpose of an open standard.
Licensing conditions that Microsoft offers for Office Open XML
Microsoft is providing the IP rights for Ecma Office Open XML under the OSP (Open Specification Promise), see www.microsoft.com/interop. You can find the actual text of the OSP on www.microsoft.com/interop/osp. It is reproduced here: Microsoft Open Specification Promise
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 (“Covered Implementation”), subject to the following. This is a personal promise directly from Microsoft to you, and you acknowledge as a condition of benefiting from it that no Microsoft rights are received from suppliers, distributors, or otherwise in connection with this promise. If you file, maintain or voluntarily participate in a patent infringement lawsuit against a Microsoft implementation of such Covered Specification, then this personal promise does not apply with respect to ny Covered Implementation of the same Covered Specification made or used by you. To clarify, “Microsoft Necessary Claims” are those claims of Microsoft-owned or Microsoft- controlled patents that are necessary to implement only the required portions of the Covered Specification that are described in detail and not merely referenced in such Specification. “Covered Specifications” are listed below.
This promise is not an assurance either (i) that any of Microsoft’s issued patent claims covers a Covered Implementation or are enforceable or (ii) that a Covered Implementation would not infringe patents or other intellectual property rights of any third party. No other rights except those expressly stated in this promise shall be deemed granted, waived or received by implication, exhaustion, estoppel, or otherwise.
Let's open up a conversation here about this behavior and about the elements of functionality referenced outside of the specification on which Microsoft Office Open XML depends.
Let's also talk about how this License functions as a contradiction of ODF, the existing ISO standard that is already doing the natural work of a universal & portable file format for office documents.