The openness of file formats

Looks like good news from microsoft (hat tip slashdot and the register), but as many people are pointing out - what does this really mean?:

• A format open for reading (making it legal for third parties to build readers)?
  
• A format open for writing (making it legal for third parties to build readers)?
  
• A format which others (e.g. a standards body) to take and modify according to public need?
  
• A formet which is not IPR encumbered in any way?
  

It's not truely open until all of the above are true - maybe they should consider adopting the open document format.