It's not. TempleOS is a famous from scratch OS created by a guy with serious mental illness. It's a sad story, but the capability of that guy was incredible. He's gone now :(
TempleOS (wikipedia) is a meme os. It's supposed to be god's os and was singlehandedly coded by the late Terry Davis. So this post isn't really marketing, and the reference is just supposed to be humorous.
I love this reaction and how dramatically out of sync it is with what TempleOS actually is. I know it is innocent and accidental so this is in no way a shot at the poster. It is just a hilariously wrong take.
I have looked it up and to include it in that list is just downright ludicrous. Let me give you some quotes from the wiki
“The system was characterized as a modern x86-64 Commodore 64, using an interface similar to a mixture of DOS and Turbo C.”
“TempleOS (formerly J Operating System, LoseThos, and SparrowOS) is a biblical-themed lightweight operating system (OS) designed to be the Third Temple prophesied in the Bible. It was created by American programmer Terry A. Davis, who developed it alone over the course of a decade after a series of manic episodes that he later described as a revelation from God.”
“The system was characterized as a modern x86-64 Commodore 64, using an interface similar to a mixture of DOS and Turbo C. Davis proclaimed that the system's features, such as its 640x480 resolution, 16-color display, and single-voice audio, were designed according to explicit instructions from God.”