I am running the pro version, and I'm running this plug-in on a production site, and also on the QA version of that same site. Both of these instances are running at wpengine.com. Prior to moving my site to this new platform I had been running it at BlueHost, and I think that the site is still running at Bluehost.com, although it is never accessed, and is blocked from being accessible to all users. In fact, I'm using your plug-in to block the site at BlueHost, while I make sure that there is nothing else that I'll need from the old site.
So, from a commercial standpoint, I'm using this plug-in on one site, and a QA site.
How should I go about resolving the error message? Do I need to shut down the bluehost site?