That's the weird thing... Why does everyone just assumes DLSS requires tensor cores to run? Sure, they accelerate the type of workload, but that's saying that games "require" AVX to run or "MMX" when they don't really need it. If you want me to be blunt, nVidia keeps the tech closed because of monetary reasons and not technical ones. Didn't they actually show it running in the non-RTX cards at some point?"Great news to a lot of people with older games with no official support and at the behest of modders. Or people that know their Developer/Publisher is in bed with nVidia."
Even if Nvidia open-sourced DLSS 2.0, it would be pointless since it requires the tensor cores to run properly. It was built on them.
So unless Intel and AMD add their own equivalent to the tensor cores in their next GPU release, it wouldn't matter if they did open source and open platform it.