The whole point of HDMI is HDCP which is necessarily very much proprietary. HDMI is a product of the film & TV industries to protect their “intellectual property”. en.wikipedia.org/wiki/HDMI
The HDMI founders were Hitachi, Panasonic, Philips, Silicon Image, Sony, Thomson, and Toshiba. Digital Content Protection, LLC provides HDCP (which was developed by Intel) for HDMI. HDMI has the support of motion picture producers Fox, Universal, Warner Bros. and Disney, along with system operators DirecTV, EchoStar (Dish Network) and CableLabs.