Sounds like your situation is exactly the type we had in mind for groov Server (you already have a Windows PC in the mix, and might want to save on cost).
Both the groov Box and the groov Server for windows will store/serve your project/pages (either in the Box or on the PC running the server). To access that server and those pages, you’d use something with a browser for the client side. Sounds like both server and client would be the on panel mount touch screen PC. Is that correct? Anything else, like a smart phone, perhaps?
Could you tell me more about you concert re: having access to the controller? (What’s the use case that worries you?)
Keep in mind, that if your R1 controller has 9.5 firmware or newer on it, there’s also a web server in there which, via the RESTful API, can serve up all your tag data. It’s just that you’ll get JSON back (meant for other devices to read, more so than humans). Vs. the groov web server (either on the PC or in the box) servers up data meant for humans to read.
But to answer our question, the only other software you need is a decent browser to act as the client.