Do you have examples of open source software in a similar situation (one company providing coordination and final approval in the previous project; similar complexity level to Gitlab, whatever that is), where that happened successfully?

I'm not challenging necessarily, I legitimately am interested in examples.

It depends on your definition of “kill”.

OpenSolaris -> Illumos

Hudson -> Jenkins

OpenOffice -> LibreOffice

MySQL -> MariaDB (not killed, but forked out of fear it would be)

And a non-Oracle example:

Node.js -> IO.js (arguable - forked because Node dev was stagnant, eventually merged)

All those had communities outside the main company long before they "moved out". What's the percentage of external contributors to GitLab? 1%?

Hmm what about the Blender project, would that one count?

I admit it's difficult to come up with examples, though I don't know of any failures either. RethinkDB has been sort of a failure, but it was never very popular to begin with.

GitHub can also be self-hosted: https://github.com/enterprise

You can't compare that as it's a paid enterprise on-prem version not something you can self-host and keep running as long as you want. You won't get community fixes for it like it would be the case if Google were to abandon Gitlab if an acquisition would be the case.

That’s not what “self-hosted” means.