the joke is that plan 9’s not UNIX, and thus does not run Jurassic Park. the absurdity arises from the fact that using such a capable operating system for dinosaur husbandry (im told this is what jurassic park is about) would be, frankly, philistine in nature.

If you look at the image from the film you will note it has the cat(?) clock of plan 9 fame. So its fairly obvious that the image is doctored.