Included in the notion of state sovereignty is the right of the state's agencies, employees, contractors and citizens to choose any type of software they want to read or write public documents. By not allowing its license to be transferred or sublicensed, Microsoft's patent license automatically prevents just about all open source software-- including OpenOffice.org--from supporting Microsoft's XML formats.
The Microsoft license basically opens it up to Microsoft software. they even excluded the end user's right to create documents. it's basically a "read only" license.