Comment by MiroslavPokorny

https://en.wikipedia.org/wiki/Apache_OpenOffice

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.

Neither https://github.com/privacyidea/privacyidea or https://github.com/eduMFA/eduMFA say either is a fork of the other.

I think you failed to share 3, 2 seem to valid examples of my challenge but the other 2 are questionable.