FWIW jOOQ's model worked great from a consumer/end-user point of view. I got to learn the whole library with no real strings attached, and then pay to adapt it/support it on Big Fucking Databases(TM) as projects required it. Their site and documentation is also quite pleasant.
In a way it feels like double-piggybacking: Microsoft, Oracle, et al. spend a lot on mindshare to make sure technical leads choose those respective stacks. Then the army of developers/consultants, required to get the promised ROI out of those stacks, inevitably have to go looking for tools. Be there to sell them the shovels. It helps if they are already familiar with it. (Free OSS adapters / "community" editions, etc., or even just very generous "evaluation" versions with no real effort to police use in a lab environment.)
Not sure how successful jOOQ has been financially, but considering they've been around for many years at this point, I have to imagine it's worked out well enough to pay for the lights and kibble?
The only other "dev tool" company I've enjoyed working with _more_ has been JetBrains. (The recent AI plugin not-withstanding.)