I agree with this - there's nothing wrong with "We're taking extensions and making them proprietary" (unless you share Stallman's belief that proprietary software is inherently immoral). There's nothing wrong with proprietary software being hosted on GitHub, having source available, accepting pull requests, allowing noncommercial redistribution, etc.
But the Redis Labs blog post was incredibly confusing when it could have just straight-up said "We're making some plugins proprietary," and this post is awfully embarrassed of the term "open core" when there's nothing to be embarrassed about. Debian, the group that is so doctrinaire about free software that it literally doesn't ship gcc's manpage by default on the grounds that it's nonfree, is happily running the open-core edition of GitLab. You're not doing something bad by saying you need money from paying customers to support the folks working on FOSS. There are lessons to be learned from previous open core efforts, and they won't apply 100%, but no lesson on successful companies applies 100% to a different situation. And they certainly apply more than 0%.
But the Redis Labs blog post was incredibly confusing when it could have just straight-up said "We're making some plugins proprietary," and this post is awfully embarrassed of the term "open core" when there's nothing to be embarrassed about. Debian, the group that is so doctrinaire about free software that it literally doesn't ship gcc's manpage by default on the grounds that it's nonfree, is happily running the open-core edition of GitLab. You're not doing something bad by saying you need money from paying customers to support the folks working on FOSS. There are lessons to be learned from previous open core efforts, and they won't apply 100%, but no lesson on successful companies applies 100% to a different situation. And they certainly apply more than 0%.