The Open Specification Promise applies to all existing versions of the specification(s)...

Future enhancements aren't covered. Adopt vanilla now, and as Microsoft improves its technology, you may be left hanging in the infringement breeze.

Even adopting the specified standard may carry infringement risk, because to implement the specification standard, you're likely to need some of the enabling technologies for which the specification calls; but that's not covered, unless you are writing software for Windows®.

Q: Why doesn’t the OSP apply to things that are merely referenced in the specification?

A: It is a common practice that technology licenses focus on the specifics of what is detailed in the specification(s) and exclude what are frequently called “enabling technologies.” If we included patent claims to the enabling technology, then as an extreme example, it could be argued that one needs computer and operating system patents to implement almost any information technology specification. No such broad patent licenses to referenced technologies are ever given for specific industry standards.

Mark Webbink, Deputy General Counsel of Linux vendor RedHat, not one to worry over small print, expressed satisfaction.

Here's ZDNet's take.