It gets installed to the hubitat hub and executes the pistons locally with no additional hardware. You can optionally install the IDE to a webserver for 100% local, but that only maters when writing the pistons so I opted out. @Roguetech wrote some great instructions to getting WebCore installed. Here is a link to his instructions I followed. They should really be placed in their own thread or sticky so they are easier to find because they are the best instructions I have found.