Cloudmin GPL vs Pro single HOST system or single MASTER-HOST system?

Cloudmin GPL only supports a single system...Master, host, everything, on one box. We haven't figured out another way to provide a clear value add for Pro (and we've gotta ring the cash register somehow to keep the lights on around here), so that's currently how we distinguish the two. I have been campaigning to change that so Cloudmin GPL can host across many systems just like Pro; but without a good story for how we encourage folks to upgrade, I don't yet have a good case to make for making that change.

And, to be clear:, Cloudmin Professional offers the following

1. Unlimited host systems (though realistically, you probably only need enough to host the number of VMs your license provides.
2. Unlimited Virtualmin systems under management. So, if you have a dozen real systems (not virtualized) and they have Virtualmin on them, you can manage all of them, without it effecting your Cloudmin hosted licensed virtual machine count.
3. All supported virtualization types; KVM, Xen, LXC, Docker, etc. You can have a host system for each one, if you want. It is non-trivial to move between virtualization types, however (though sometimes images can be moved between, depending on a few variables). Realistically, you probably want just one..or maybe one full virtualization type and one container type, if you're on-board the container hype train.
4. Cloudmin Connect features, which includes Cloudmin Services for Virtualmin. This allows hosting your DNS, databases, and spam/AV scanning, on central boxes shared by all Virtualmin systems (whether GPL or Professional).

Cloudmin Pro has a lot of cool features, is what I'm trying to say, and we probably are getting to the point where there's enough to differentiate it from GPL without having host/VM limits on the GPL version, and to convince a significant number of people to upgrade (if they know what it gets them).