DisplayPort is a popular system on Apple Macs, and is also used by some Dell monitors and Toshiba notebooks.
Notes HDMI Org (via TR):
The HDMI specification defines an HDMI cable as having only HDMI connectors on the ends. Anything else is not a licensed use of the specification and therefore, not allowed.
All HDMI products undergo compliance testing as defined by the Compliance Testing Specification.
The CTS clearly defines necessary tests for all products defined in the HDMI Specification. Since this new cable product is undefined in the Specification, there are no tests associated with this product. It cannot be tested against the Specification.
HDMI Org does say they agree there is a need for these kind of cables, but they do not see how to make "a licensed version" anytime soon.