It depends on your definition of "open." The HD DVD specification is created by the DVD Forum (which is comprised of many different companies) and not by any individual company, although of course any given section of the specificaion originiated from a proposal made by one or more individual companies. Case in point: the interactive layer was proposed by Microsoft and Disney, but it was accepted by all companies and the final version in the specification has had contributions from other companies such as Sonic Solutions and Toshiba. The point being that no single company controls the format; the other member companies must agree to the proposal in order for it to pass. Clearly this doesn't meet some definitions of "open" since the specification is still covered by copyright and implementing it requires paying royalties, etc. but it is also not wholly proprietary, either.