If it was a commercial project I imagine there would likely need to be other staff involved, and adoption would be lesser. Whether that ends up being more or less money for him in specific in the end (or whether the project/company would survive) is not without question, in my mind.

Not necessarily. I would expect part of the reason it's one of the most used is because it's non-commercial.

I do agree it's not fair compensation, though.

I might suggest for a company to use VueJS since it is open source and donate but I’m never going to suggest that a company bases its product on Telerik components.