Comment by ocdtrekkie

Nobody can "abscond" with what you've made. It's always yours, it's always accessible to you, and you can always make it better.

Yes, if someone else comes and extends your work and eclipses your production, they're able to decide what to do with it as they want. That's the key point of being open: Letting people do what they want with it.

If anything, I'd contest the claim that copyleft can be considered open source any more than a license that lets you look at the source but doesn't let you modify it. Copyleft controls the source and forces your views on people who want to use it.