Sure, well, I wrote that in the context of, if any GPL software developers want their software to be used more in a non-copyleft setting and are willing to nego

Sure, well, I wrote that in the context of, if any GPL software developers want their software to be used more in a non-copyleft setting and are willing to negotiate a difference license. It very well could work both ways; some proprietary software developer would likely be willing to release their software as GPL if paid enough money, since, ostensibly, the proprietary license was chosen to help make money in the first place. I can imagine that some proprietary software developers choose proprietary licensing for some other reason, but I suspect it's mostly the default for anyone looking to charge for copies.