With no copyright everything would be effectively under CC-SA (or CC-SA-BY in countries with "moral rights"). That's weaker than the GPL because it doesn't include the "preferred form for modification" and weaker than the GPL3 because it doesn't include the anti-TiVoisation clause, and the common F/OSS patent protection clauses wouldn't work (but presumably there would be no applicable patents either).
However, you can also fake copyright, by releasing something subject to an NDA that the recipient will undertake not to redistribute it except as listed, with their ability to access your secret literature as their consideration to make a valid contract. The major difference is that it would only allow you to sue the first person to release your item, not all the subsequent redistributors who never agreed to your contract.
Biting the hand that feeds IT
