I wonder where you get a good commercial license to use like this. Is it always a custom thing requiring expensive lawyers or is there some repo of commercial licenses one can use?
Now, from a practical point of view, that may be perfectly fine for him. If he's not getting many contributions anyway and doesn't really care about it, funding the project through license sales can make sense. Sometimes I think people don't think about the trade off that's required, though. I've seen people get frustrated with the lack of outside participation.
However, I agree with you. In this case, it seems like a smart move.
It's not copyleft, but if you ask you might be able to use it that way.
Selling copyleft exceptions works fine with existing free and open source licenses.