Short answer: Right now, it's just available on Fantasy Grounds. We're working on others, subject to demand/feasibility. Contact us if there's a VTT you'd particularly like to see them for. Not much more to say on that, really – I do the conversions myself and am working on other formats, but each VTT does things its own way and has its own considerations, and there's often a process you have to go through to be able to sell conversions anyways. It all takes a good chunk of time and it's a balancing act of working on new content and doing stuff like this. Given this is our first conversion, we also don't know how much demand there is for VTT conversions as a whole and for XYZ tabletop. Drop us an email if there's a tabletop you'd particularly like to see stuff for and we'll look into it. Foundry and Roll20 feel pretty likely.