That's not Gridcoin which should determine private from public. It's up to the institute itself, or better the project in question, to declare itself public or private at sign up. If they declare themselves as public then all is like before (they don't profit from a particular growth in network population ). If they declare them private then they should provide a guarantee that Gridcoin workers will be well rewarded to compensate Gridcoin tax. And then they profit from a big network of hungry crunchers!