This isn't really the "open core" model if the core is not actually open. GP would like to contribute these features themselves to the open core but GitLab likely would not allow it.
I don't agree with this assessment. Open Source does not require that the maintainers will allow you to push changes upstream that they don't like. Is AOSP not open source? Chromium? Atom? Linux? Linus rejects a lot of stuff.
Now, it may be poor stewardship if valuable changes are rejected, but Open Source is about your freedom with the code, not the willingness of the project maintainers to commit your pet features.
But absolutely nothing is preventing you from using a a fork of CE which adds every EE feature so long as they were developed independently of the closed-source EE code-base.
Open source doesn't mean the maintainers have to accept your patches.
