It works by allowing the project to deal with honest people and ignore assholes efficiently.
And for a small team (in this case, one person), getting rid of assholes who just want to rip the project off with minimal effort is a big win.
After all, if you just want to play around with the system you are a hobbyist and can get it for free anyway. Why go to the extra effort of stealing the code?
And if you actually are creating value with the system, don't you think you might want some support?
If your answer in either case is that you would rather cheat the author then there is nothing tangible stopping you, but you just defined who you are and selected yourself out of the class of people the maintainer has to deal with.
I don't think it is about people being assholes, but just going the way of least resistance. So if it is easier to buy a license key and use it, than to just remove the license check, then that's what people will do. Same the other way around.
I read somewhere here that the free version is restricted (single thread only?). Also the mechanism for offline work sounds like a pain, so if multithreaded and offline is your use case, the case for getting a license key just got murky.
I am wondering about this because it just seems hard to sell source available software. Everybody is complaining about price and license keys. But if you put the software behind an SaaS, and go the subscription way, you avoid all of this trouble. Of course, in this case, that just doesn't seem possible.
Personally, I'd like to sell my software source available and without an SaaS indirection, but I am wondering how to get paid in that scenario.
License keys make the software worse, so there just seems to be a logical problem here in the case of source available software: Why pay for worse software? In case of closed-source software, no such logical problem exists: license keys make the software infinitely better, because otherwise it wouldn't work at all.
I forgot the main point of my reply. If this is about filtering for honest people, why require a license key at all, especially one that needs to be checked online? Honest people will pay for the license even if no license key is necessary, right?
And for a small team (in this case, one person), getting rid of assholes who just want to rip the project off with minimal effort is a big win.
After all, if you just want to play around with the system you are a hobbyist and can get it for free anyway. Why go to the extra effort of stealing the code?
And if you actually are creating value with the system, don't you think you might want some support?
If your answer in either case is that you would rather cheat the author then there is nothing tangible stopping you, but you just defined who you are and selected yourself out of the class of people the maintainer has to deal with.