> You should check out this thing called open source software

Open source actually demonstrates that copyright serves a purpose. There are still customers for non-open software, even when open alternatives exist, so the ability to monetize brings new offerings to the economy.

You should check out this thing called GPL that is the standard license of open source projects like Linux, and heavily depends on copyright laws.

Or are you suggesting open source software is public domain?

Open source software is unique in that it takes little to no capital investment to create. People post free art too. It doesn't mean that Game of Thrones didn't cost anything to produce.