By default, Fedora only includes free and open source software. However, with the introduction of these curated third-party repositories, users can opt-in to enabling selected extra sources. Some software in these optional sources is proprietary, and may have restrictions, including access to the source code. Read on for more information on how this works. This brand new feature is part of the upcoming Fedora 28 release. However, recent updates to Fedora 27 provide changes to easily enable these repositories as well. Some of the third-party sources contain software that can only be installed on Fedora 28.