I think he was under the impression that using the GPL (instead of a BSD license) would avoid commercial forks. Personally I don't care, Gentleman doesn't care, and the Revolution people (some at least) are pretty good guys.
But leading with the above would be shitty click bait }:-)
They would avoid proprietary forks (not commercial, that's not the same thing) if they actually defended the damn GPL. Instead, they kept weakening it, kept trying to change the API from GPL to LGPL (and I think they actually did it) and encouraged non-free plugins on CRAN.
The license will need to a better job of protecting work
donated to the commons than GPL2 seems to have done.
But leading with the above would be shitty click bait }:-)