Hopefully it helps calling out attention to this in a separate thread.
In http://lists.w3.org/Archives/Public/public-webapps/2010AprJun/0043.html Maciej states Apple has no interest in implementing UMP from the UMP specification. (I believe this means that a CORS defined subset that roughly matches UMP is fine.) They want to retain their CORS support.
For Opera I can say we are planning on supporting on CORS in due course and have no plans on implementing UMP from the UMP specification.
It would be nice if the three other major implementors (i.e. Google, Mozilla, and Microsoft) also stated their interest for both specifications, especially including whether removing their current level of CORS support is considered an option.
-- Anne van Kesteren http://annevankesteren.nl/