The Linux operating system is an example of freeware.
Origin of freewarefree + -ware
freeware - Computer Definition
Software given away free of charge, typically over the Internet or through a user group. Individual software developers often make beta versions of copyrighted software available as freeware for user trials, but charge for subsequent versions refined as a result of end user input. Some developers never charge for its use and even forbid others to do so. Some freeware is available in commercial versions, with charges for support, but not for licensing. Freeware is generally not public domain software, as there usually are restrictions on its use and modification. See also beta, copyright, open source, public domain, and software.