To some extent I would argue that Linux is a spiritual fork of Minix and Unix.
But I think it’s also worth pointing out that these were in vastly different times where a single person or a small group of people could maintain an OS. An OS or browser is vastly more complex now.
It was a bit challenging long before that. I ran webhosting on FreeBSD in the early 2000s - remember finding a tool you needed and hoping it was in ports?
The point which i didnt not mention in my original question is that merging from the fork is a pain, which is why its just easier to jump onto and continuing development on the fork if it gains traction.
The amount of people that to this day still default to OpenOffice and have either never heard of LibreOffice or think it's the same as OpenOffice is crazy making though.
Difficulties maintaining a sufficient number of contributors to keep the project viable have persisted for several years. In January 2015, the project reported a lack of active developers and code contributions.[49] There have been continual problems providing timely fixes to security vulnerabilities since 2015.[50][51][52][53] In September 2016, OpenOffice's project management committee chair Dennis Hamilton began a discussion of possibly discontinuing the project, after the Apache board had put them on monthly reporting due to the project's ongoing problems handling security issues.[54][55][56]
Sounds like AOO is effectively dead, so this example is a fail to my challenge.
OpenSearch & ElasticSearch both seem alive, as well as OC & NC.
AOO became a thing after LibreOffice essentially won.
Before that it was OpenOffice.org owned by oracle, forked into LibreOffice in 2010, with LibreOffice getting significant traction and Oracle throwing in the towel and donating OO to Apache Foundation in 2011.
If AMZN couldnt make their fire whatever it was called fork of Android really grow, what chance has the community got ?