Where do I download the software to experience LIMINAL?

LIMINAL runs on a Creative Social VR platform called Resonite. It's completely free and you can download it here: https://store.steampowered.com/app/2519830/Resonite/

Do I have to be in VR to experience LIMINAL?

No! While VR is the recommended way to experience LIMINAL, you can also join the experience via "Desktop Mode". Simply select "Play in screen mode" when you start Resonite.