About
Nexuiz is a free first-person shooter by Alientrap, released in 2005 under the GPL using the DarkPlaces engine, a modified Quake engine; a separate commercial remake also called Nexuiz was later released for Steam and Xbox 360 using CryEngine 3. Xonotic is an arena-style first-person shooter with a wide array of weapons, continuing from the original GPL Nexuiz codebase. It's cross-platform (Linux, macOS, Windows), fully open source under GPLv3+, supports online multiplayer, and includes modding support for custom maps and scripts; development happens primarily on GitLab, with most work in the xonotic-data.pk3dir repository.
How it differs from the original
Xonotic continues as the free, community-developed successor to the original GPL Nexuiz codebase, distinct from the later commercial Nexuiz remake built on CryEngine 3 for Steam and Xbox 360.
Getting started
Stable releases and compiled binaries are available from the official download page, with beta autobuilds also offered; source code can be compiled by following the instructions on the project's GitLab wiki.
History
Xonotic originated as a continuation of the free, GPL-licensed Nexuiz codebase after the Nexuiz name and IP were used for a separate commercial CryEngine 3 remake.