It is currently based on the NXT platform, but we're hoping to move to Ardor when it's launched.  Unfortunately it's not yet clear if that will be possible, as communications with their team have indicated that only select child chains will be permitted.

I did originally look at Ethereum (6 months ago), but I found their platform to be buggy, expensive and slow.  Not yet as robust or mature as the NXT/Ardor platform.

I'm already assessing alternatives, in case it turns out that Ardor won't work for us.