The Nvidia proprietary bit does leave HLLs like Furhark or DSLs like Neanderthal a bit of an advantage. Are there ways of doing portable GPU things with Julia?
The Julia array abstractions make it so that most code is vendor-neutral already, and you execute on whatever GPU back-end you want by using an appropriate array type. For vendor-neutral kernel programming there's GPUArrays.jl and KernelAbstractions.jl, but both aren't currently very user friendly (but are actively used as a building block for user-facing applications and APIs).