The developer of shareware generally asks for a small donation or registration fee if you like the software and plan to use it. By registering, you may receive further documentation, updates and enhancements. You are also supporting future software development. Sometimes authors dedicate their software to the public domain, which means that the software is not subject to any copyright restrictions. It can be copied and shared freely.
Freeware enters the public domain from many sources.
Its presence there suggests that the copyright has been surrendered. However, unless authors explicitly state that this has been done, they still hold the copyright to the software. This means that although they are letting you use it, they still actually own it.