'responsibly'=stumble upon security bug(s) and report them
again, definition of 'stumble upon'?
Is that in day to day use? fuzzers? Stress testing? ........
I agree with Manu, without Do's and Don'ts drawing a strict line in the sand it still upto Microsoft to determine what the accept as responsible. If they define responsible as only reporting issues discovered during normal use then this isn't related to 'hacking' ethical, responsible or otherwise.
To me this article seems like PR fluff and doesn't change a thing.