GPL is not a "type of copyright"; it's a license that derives its power from copyright. The same is true of pretty much any license that tries to limit what you can do -- which includes most open source licenses (BSD, MIT, Apache).

There are also open source "licenses" that essentially place the code in the public domain. These are the only ones that fit the article's description.

Unfortunately the public domain concept is not recognized in all countries. If you wish for your software to be truly available in these nations you will still need to apply some sort of copyright license, no matter how liberal.

Even open-source software has a potential problem in some countries. For example, while OSS is often received free of charge, the government can argue that the user still got an item of value. So they have to pay taxes on this "gift".

That's most definitely incorrect. And it's not just a technicality; copyright law is the legal foundation of free/open source software.

You can also charge for open source software.

Also, I believe if you find a free piece of open source software that is useful to you, one that comes free as in free beer, then you should be donating to the developer/s; even if its just enough to buy them a beer. Show the developer a little gratitude.

If you don't feel like going that far, even a thank you note is really appreciated.