You can release a binary as public domain. Also, I believe that public domain as a concept does not exist in some countries. if i remember correctly the conce

You can release a binary as public domain. Also, I believe that public domain as a concept does not exist in some countries. if i remember correctly the concern is that without a license the original author could change their mind and sue. But any public domain software also matches the fsf and osi definition of free software and open source respectively. Atleast in jurisdictions where public domain exists. You may be confusing things with copy-left, which is designed to protect users from developers. The gpl is a copy-left license.