Which type of software is unlicensed without copyright protection?

Public domain software is not subject to copyright protection, making it unlicensed. This means that anyone can use, modify, and distribute it without seeking permission or paying royalties. Public domain works are typically released by the author to the public, intending for them to be freely available and utilized by anyone.

In contrast, proprietary software, shareware, and commercial software are all protected by copyright. Proprietary software has restrictions on its use, distribution, and modification, typically requiring a purchase or license agreement. Shareware is a type of software that is distributed on a trial basis, often with the expectation that users will pay for it if they decide to continue using it after the trial period. Commercial software is also protected and generally involves a purchase for use, with licensing agreements that govern how the software can be used.

Thus, public domain software stands out because it lacks these restrictions, allowing for unrestricted access and usage by anyone.