i don’t think adc was encumbered by patents, at least not in any way that prevented other manufacturers from making use of it. it wasn’t locked down behind special handshakes and a certification program like lightning is. it used the same signaling protocol that dvi ended up using, which is why passive adapters like the belkin one above were possible. the additional pins on the connector were used for power and usb. the specifications were freely available, and monitors, gpus, and kvms were released that used the connector in the late '90s and early '00s.
the problem people are haivng is that this connector did not see wide use, so cables and adapters are hard to come by 25 years after the fact.
putting vesa in charge wouldn’t change anything here unless vesa decided to ditch dvi and push this connector instead. however, that probably wouldn’t have happened, because their constituents (most wintel pc makers) would have preferred the cheaper solution of not bundling video, power, and usb in a single cable.