Permissive licenses like "if you use this code you must also make your code available under the same license" form the basis of the world's most often used open source software.

Open licenses are not the same as abolishing copyright.

Those are not permissive licenses. Those are copyleft licenses. As I said, a lot of software uses permissive ones.

https://blog.ipleaders.in/permissive-license-copyleft-possib...

“Permissive” provided the code is attributed, which the products you advocate for do not do.

Those licenses only carry weight because of copyright.

I was talking about permissive licenses. They have very few conditions:

https://blog.ipleaders.in/permissive-license-copyleft-possib...

Their weight is irrelevant. They would carry pretty much as much meaning in the complete absence of copyright.

In the world of sensible defaults they wouldn't need to exist at all.

Software licenses exist because copyright enables author to dictate terms. Without that, there are no software licenses. This is where the "without copyright, there is no OSS" comes from.

> Their weight is irrelevant.

I think we're having different conversations. The only thing I'm talking about is whether terms can be legally enforced without copyright.

I'm not sure what you're getting at, but it seems to be something like "Permissive licensing is basically like public domain." I don't agree with that line of thinking because of the attribution requirement in permissive licenses, but if that's what you're getting at, I get what you mean.