Which category of software is protected by copyright laws but is available at no cost?

Closed-source software refers to programs whose source code is not made available to the public. This type of software is typically sold or licensed, meaning users must pay for it and cannot modify or redistribute it. Thus, closed-source software directly contradicts the notion of being available at no cost.

Shareware is a distribution method that allows users to try software for free for a limited time, after which they are encouraged to purchase a license for continued use. While it may start as free, shareware is not entirely free since the user is expected to pay after the trial period, making it distinct from freeware.

Public domain software is no longer under copyright protection, meaning it can be freely used, modified, and distributed by anyone without restrictions. Unlike freeware, public domain software does not have an owner, and thus does not have the same copyright protections associated with it.