Even if he shuts down the emulator, the code is out there forever. He will be playing whackamole with forks and various other projects just like Nintendo does. The analogy absolutely works for what's happening.
That's exactly why they're changing the license. The problem with Swanstation are the developers. Retroarch in general has some pretty horrible people maintaining it and this isn't the first time they've harassed an emulator dev over nothing.
And "it is already out there so they can't take it away":
swanstation is already a few versions back feature wise? But, regardless, it will rapidly become outdated as new "tech" is added to emulation and issues are found with third party libraries or code. Good software needs good support and just having a ten year old hash is almost always worse than useless.
Is that really even true of emulators of old consoles? There's not a lot of new features coming out for the original PlayStation. Either way, part of the reason that SwanStation is dead is that it's not even the best libretro PS1 emulator anyway.