Earlier quoted context omitted.
People are free to fork Unreal. People can continue working on Unreal even if Epic stops devoting reosurces to work on it.
How? Unreal is not FOSS. You have access to the code, but the license doesn't allow changing it legally afaik
By hitting the fork button on github.
>but the license doesn't allow changing it legally afaik
It does allow you to make own changes to it and share it with other licensees of the version you forked from.