How is that a bad thing? I think that's a zero sum game way of looking at it.
No damage is done if someone makes a closed source version. They can add value and stimulate competition. More often, they fail.
Occasionally, core developers may enrich and provide additional functionality upon a permissive core. Why not look at Postgres as an example?
And what harm is done? Lost code contributions? Some have no interest in collaborating on software they can't incorporate / copy from later without restriction. It takes time to wrap ones brain around a codebase.
Why would someone take time to understand the internals of a GPLv3 app, when they could never incorporate pieces of it in their code later on?
> it's ideal for applications like this.
Ideal is subjective. Judging by the above, it seems as if enforcing envy trumps programmers doing as they wish with the code.