Alternatives and similar repositories for addons:

Users that are interested in addons are comparing it to the libraries listed below

• fx02 / cndoom
  Competition Doom is a Doom source port used for recording speedruning demos.
  ☆8Updated 2 years ago
• Kroc / DOOM-Crusher
  Shrinks DOOM resource files: PK3s (ZIP files), WADs, PNGs & JPGs.
  ☆15Updated last year
• SoDOOManiac / So-Doom
  So Doom is about adding features to Crispy Doom that Fabian won't implement :)
  ☆23Updated 8 months ago
• LordMisfit / NR-IotDM
  Naferia's Reign: Invasion of the Dark Mistress (For Duke Nukem 3D: Atomic Edition w/ EDuke32)
  ☆11Updated 5 years ago
• maraakate / daikatana
  The unofficial Daikatana 1.3 patch including Linux- and FreeBSD-Ports
  ☆11Updated 2 months ago
• fgsfds / Liquidator-3D
  Russian Build Engine game translated to English and modified to work with modern ports
  ☆22Updated 5 months ago
• emileb / gzdoom
  GZDoom adds an OpenGL renderer to the ZDoom source port.
  ☆13Updated 2 weeks ago
• fgsfds / Legend-of-the-Seven-Paladins-3D
  Unofficial English translation of the Taiwanese 1994 FPS and the very first game ever made using Build Engine
  ☆16Updated 4 years ago
• Hendricks266 / SWP
  A Shadow Warrior Port by ProAsm
  ☆16Updated 6 years ago
• LukeKenTeam / LukeKen3D
  Free assets and Free Open Source Software game for based on Build Engine of EDuke32 and DN3D engine.
  ☆11Updated 6 months ago
• drbelljazz / marshmallow-doom
  Gameplay-oriented fork of Crispy/Chocolate Doom source ports
  ☆11Updated 10 months ago
• HandsOfNecromancy / HandsOfNecromancy-Engine
  ☆10Updated 2 months ago
• nashmuhandes / WidePix
  Widescreen graphics replacements (up to 21:9) originally made for GZDoom. Supports Doom, Heretic, Hexen, Strife, Hacx, Chex Quest and Har…
  ☆30Updated 3 years ago
• Shanjaq / uhexen2
  GitHub clone of SVN repo svn://svn.code.sf.net/p/uhexen2/code/trunk (cloned by http://svn2github.com/)
  ☆12Updated last year
• Sakitoshi / mbf_sigil
  Marine's Best Friend Doom sourceport with added Sigil support
  ☆19Updated last year
• AloXado320 / sm64ex-alo-patches
  A series of patches made by various people for my fork, more details in the Google Docs page https://github.com/AloXado320/sm64ex-alo
  ☆9Updated 3 years ago
• yquake2 / ref_vk
  Optional Vulkan renderer lib for Yamagi Quake II
  ☆51Updated last month
• nashmuhandes / SpriteShadow
  Universal mod for GZDoom that adds shadow sprites underneath actors.
  ☆24Updated 3 years ago
• eukara / freetfc
  Clean-room reimplementation of Team Fortress Classic in QuakeC.
  ☆25Updated 8 months ago
• yquake2 / zaero
  A port of Team Evolves Zaero to Yamagi Quake II
  ☆28Updated last month
• drfrag666 / zdoom32
  Highly moddable Doom engine with support for all Doom engine games
  ☆11Updated last year
• Blue-Shadow / nc-shc
  ZDoom special lumps syntax highlight configurations for Notepad++ and TextPad
  ☆15Updated last year
• dibollinger / amcduke32
  Fork of eduke32 for the AMC Squad.
  ☆12Updated 2 weeks ago
• jekyllgrim / Painslayer
  Painkiller mod for GZDoom
  ☆37Updated 2 months ago
• Styd051 / DOOM64-Super-EX-Plus
  this is a version custom fork of EX+ with new custom contents for DOOM64
  ☆23Updated 5 months ago
• hogsy / chronon
  This is an open-source reimplementation of Anachronox, built on top of the Quake 2 engine (which funnily enough is the same engine Anachr…
  ☆50Updated 2 months ago
• RedemptionEngine / redemption
  GZDoom fork that focuses on changing non-negotiable aspects of GZDoom for QOL purposes
  ☆11Updated 3 months ago
• neogeographica / quakestarter
  A package with tools for setting up a playable Quake installation and downloading/playing/managing many highly-regarded addons.
  ☆22Updated last year
• SpiritQuaddicted / reQuiem
  reQuiem is a custom OpenGL Quake engine for Windows and Linux. It's designed for maximum compatibility with all things Quake - past, pre…
  ☆17Updated 10 years ago
• NightFright2k19 / duke3d_widefix
  Widescreen Fixes for Duke Nukem 3D
  ☆36Updated last year