The blog post attributes the list of design principles to Mike Gancarz's "Unix Philosophy" (1994) whereas ESR's book "The Art of UNIX Programming" was published

The blog post attributes the list of design principles to Mike Gancarz's "Unix Philosophy" (1994) whereas ESR's book "The Art of UNIX Programming" was published in 2003. I'm sure those ideas had been floating around in the community for a long while but was written down more formally in those books.