That problem is not that it's not open source, the problem is that for a start it's invisible!
Don, if you are suggesting that OOXML is an "Open Standard", we can continue the discussion if you can point to a complete copy of the current draft of the standard. You know, the one the BSI supposedly voted on. The BSI seem to have voted on a nonexistent draft.
Not only does it appear the BSI voted without having seen the thing they were supposedly voting on, but also it appears that that draft is _still_ not available.