Apple and Microsoft are the two most likely parties to do so here. This isn't a theoretical risk.
I'd honestly rather Apple and Microsoft ripped off my work if it meant that my work provided more utility to a larger number of people.
You should watch his talk:
https://www.youtube.com/watch?v=MkJkyMuBm3g
(He used to be a maintainer of busybox, a GNU clone for embedded devices. He then ended up writing toybox, a similar project under the more free MIT license.)
I can take a guess with respect to Linux: that's the kind of software where forcing companies to submit code back to it is enormously beneficial due to the need for an operating system to have drivers for vast ranges of different hardware.
That "friction" is by design. It prevents someone else from screwing over the users.
The people that oppose copyleft are those it was specifically design to protect against.
Copyleft protects the user. The friction is, like you said, by design. It ensures that something that started free, stays free, and can't be rug pulled out from under you.
Big monied interests have been trying, and succeeding, in changing the discourse around free software away from free and to simply just "open source" and moving toward permissive licenses, specifically so community effort can be extracted and monetized without contributing back.
And in some of those cases GPL wasn't enough to prevent it. Niche end user utilities, where original is available for free have little room for monetization. And in many cases existing users are already choosing the open source option despite the existence of commercial solutions, or where it's too niche for commercial solutions to exist.
Only thing that comes to my mind is VScode with all the AI craze. But that doesn't quite fit the pattern neither is the Microsoft underdog, nor it's clear that any of AI based editors derived from VScode will survive by themselves long term.
There are also occasional grifters trying to sell open source software with little long term impact.
VSCode is a proprietary fork of code-oss, the product located at https://github.com/microsoft/vscode. It might not be an example that you're looking for though.
I suspect that those who express concern over your work being ripped off are just showing that they are extremely happy with how you run things. Rather than being under the control of another entity, the actual value is in your personal involvement. That's just my two cents, I hope I'm not putting words in anyone's mouth.
EDIT: I realize that you aren't the creator of Ghostty, but my original statement seemed like I was stating this.
I don't think there is any citation needed. Linux powers all the cloud providers, 80% of the mobile market, a ton of random devices. At this point Linux is the most important OS on the planet, ahead of Windows and Apple OSes. It's just not as visible.
Also, though, GCC got Objective-C support, and still has it, because the FSF told NeXT it would violate the GPL for them to attempt to make Objective-C a proprietary add-on to the GCC compiler, even if it wasn't literally linked with it. And a lot of GCC backends probably would have been kept proprietary by one or another hardware company if the license had allowed it.