I think copyleft was a mistake. I don't understand the value of it beyond increasing the reach of open source, it has no direct benefit to the source. It imposes a higher cost than if you just charged for the license. Not to mention the cost to the publisher of enforcing it.

Open source is about freedom, that should include the freedom of consumers to make whatever choice fits their target. If we want to increase its reach, we should emphasize the value of that freedom. People have a strong instinct for reciprocity and it is strongest when it is entirely their choice.

That presumes consumers have a choice to make in maintaining that freedom.

For a concrete example look at OpenWRT, there were not many good choices before copyleft forced the linksys release. Now they have exploded and there is an entire ecosystem of open software and modifications on routers.

Copyleft is about freedom of consumers to make whatever choice fits their target, unlike permissive licensing, which is about freedom of corporations to take away freedom of consumers.