It's worth noting that OpenSimplex has different characteristics to Simplex in higher dimensions. Specifically some have noticed a stark tendency to form orbs i

It's worth noting that OpenSimplex has different characteristics to Simplex in higher dimensions. Specifically some have noticed a stark tendency to form orbs in 4D, so it's definitely worth comparing the output of all 3 (perlin, simplex, and OpenSimplex) to see if they give you what you're looking for. Additionally, it may or may not be legally distinct (hasn't been tested).