I'm having a hard time interpreting the claims found in Ken Perlin's patent for simplex noise. It seems that if I do not use the same method of hashing indicies that he used, I'm not violating claim 1. Claim 2->6 on the other hand seems very broad, it seems the very idea of using simplexes at all in any procedural noise generation would violate the patent claim on 2 -> 6, especially number 5:
producing the images with texture that do not have visible grid artifacts with the computer by decomposing a hypercube into n! simplices, where each simplex corresponds to
an ordering of an edge traversal of the hypercube from its lowest vertex (0,0, . . . , 0) to its upper vertex (1,1 . . . , 1), where n is greater than or equal to 3 and is an integer; and displaying the images on a display.
Which to me reads, "You can't use simplexes for any dimension above 2 when generating noise". I'm not sure how OpenSimplex Noise gets away with this because despite using a different method of simplex generation, it is still actually using simplex decomposition and hypercubes.