URScript is a python like language that is used to control universal robots. You don’t need to know it to program a UR, as you can just use ordinary program nodes for that, though it is useful when you need to program more advanced functionality. It is not required to run a simulated UR5 on a windows machine, as it is only used by polyscope.
The easiest way to setup and start running a universal robot simulator from a windows 10 machine is to download a VirtualBox and setup a virtual Ubuntu64 machine, using the URCaps Starter Package.
Once you have got the virtual box up and running, open a terminal, navigate to the ursim folder, then to the version of polyscope you wish to run, and execute start-ursim.sh UR5
Hope this helps.