Welcome to the forum @Elindo586.
Node-red is free and open source.
Flowfuse are the principal maintainers and have a commercial product which extends Node-red but you certainly don't need to use the Flowfuse product.
A more feasible way to start...
IMHO the simplest is to use a Debian based Linux machine and the "official" installer script.
If you want a dedicated computer, the cheapest to comfortably run Node-red is the Raspberry Pi 2 Zero.
You don't need the full desktop OS, the lite version is fine, and you can access it over ssh from any computer so no need for a monitor and keyboard.
Installation instructions are at Running on Raspberry Pi : Node-RED.
There are lots of posts here related to communicating with industrial machines over modbus or similar.
You might want to install the Mosquitto MQTT broker on your Node-red machine too.
There are a few videos on Youtube for beginners. Search for "Introduction to Node-red"
