But then they jack up the price a hundredfold.
You can't do anything (short of rewriting), even if you could flat-out hire a replacement dev team for the entire project for cheaper than what they're charging you.
OpenOffice and MariaDB are classic examples of Free Software solving this - the IP holder sandbagged, so the community forked and fucked off. Even despite that though, LibreOffice still suffers from losing its OpenOffice name, and plenty of users lose out because they're unknowingly using a barely-updated version due to abovementioned sandbagging.
Proprietary software hands a default victory to the IP holder. Free Software hands a default victory to the user. It's either one or the other.
More likely it would implode the open code available, since usage would drop like a rock.
1) Once you're required to pay money, people start comparison shopping and proprietary software is optimized to win that game.
2) Nobody wants to spend the engineering, accountant, and lawyer hours to keep track of assorted semi-commercial licenses for a zillion dependencies and what they're owed. Half the point of FOSS is that you don't have to keep track of licenses and compliance, as the periodic sob stories on HN/Slashdot about "Oh no, I got audited and wasn't in compliance and had to pay. I'm going to switch everything to FOSS; that'll show them!" show.
Uh, he's okay with selling exceptions.
I could be wrong but it seems obvious to me that semi-commercial licenses would explode the amount of open code available, because instead of devs working for corporations, corporations would end up working for them.
Commercial licensing - open code, free for non-profits, per-seat or per-user pricing for for profits with an official license, forks are considered a derivative work, clean room clones aren't. There would be details, but there are always details, and they don't stop two hundred page EULAs from existing and being (mostly) binding.
But we don't have this because Stallman is a zealot and he wanted to Make A Point about purity. So instead of creating a market where devs could actually get paid for original work and corporations would be the ones paying, corporations get millions of hours of development effort for free - because he thought he could somehow magically strong-arm them into playing to his rules.