[bobdvb]

No, the connectors wouldn't be regulated, you're not violating any IP by buying them and there's no prohibition on any of the manufacturers selling them to unlicensed companies. At worst you can assert a patent against the design but there's no specific patent for that design, there are patents for some aspects of the design/implementation but they're hold by the manufacturers of the connectors themselves.

There have been many examples in the past of consumer electronics companies selling things that are electrically and logically compatible with HDMI, but they just have to avoid using the word HDMI.

Probably one thing that the HDMI forum is holding over AMD/Valve is that there's an API to manage some of the functions of the HDMI driver. They could infer that this API is a part of the closed standards of HDMI Forum. But 90% of the threat is about certification and branding I am sure.