Because I love F/OSS, the open-source strategies that I like best don't involve any code not being available under an open-source license, e.g., dual-licensing

Because I love F/OSS, the open-source strategies that I like best don't involve any code not being available under an open-source license, e.g., dual-licensing (Qt) and pure support models (Red Hat). And I also agree that open-core ultimately means proprietary software, if you need the whole shebang. It also means that certain features will never be accepted into the core product even if the community develops them, because they'd bridge the software vendor's moat. But I don't think either not-fully-free-but-related-to-open-source model is as disappointing as the rug-pull of a license change itself. Aside: I think BuSL can be a great license for software that's not part of any customer/user's way of earning a living. Id Software basically used to informally use a similar scheme for all their game engines (and maybe still do?), where the engines get released as F/OSS some number of years after the game comes out, and that has ended up enabling the development of lots of good open-source games and game engines. It can basically undo the damage caused by our insanely long default copyright terms. Not the same thing as providing open-source code up front, but still a very pro-social thing to do.