I agree but part of the marketing strategies (specially for Cisco, but im afraid HP will follow) is to do their best to lock in their customers.
This way not only the switch/router must be replaced but also all the optics and now the dacs aswell - which will be more expensive than just replacing the switch/router itself.
However having a DAC that identifies itself as some valid HP partnumber along with some valid Cisco partnumber on the other end sounds like something a 3rd party optics vendor should be able to perform.
Tried asking www.flexoptix.net or similar?