I disagree for two reasons. The first is that if the traditional upstream stops caring about improvement, it's only reasonable for other parties to move on. A

I disagree for two reasons. The first is that if the traditional upstream stops caring about improvement, it's only reasonable for other parties to move on. And that's largely true with the C ecosystem, as it was with OpenOffice for example. Second, "extend" has traditionally meant "extend with proprietary code". Think early 2000s Microsoft with browser APIs and J++, or Amazon with their in-house forks of MongoDB, PostgresQL, etc. There's plenty of innocuous activity that could be called E3 if you stretch the definition that far. Most of the GNU ecosystem for example.