What is difference between Extender and OpenXcom?

[aziza]

What is the difference between these 4 mods?
Do you need to go through them all to get the full experience?
or are they 100% duplicated between each other?

1 UFO Extender / X-Com Extender
2 Enemy Unknown (1994) Extended
3 OpenXcom
4 OpenXcom Extended (OXCE)

[Meridian]

#2 Enemy Unknown (1994) -- is the original game (https://www.gog.com/en/game/xcom_ufo_defense), there is no "Enemy Unknown (1994) Extended"
#1 UFO Extender / X-Com Extender -- is a fan-made patch for #2 (https://www.ufopaedia.org/index.php/UFOextender)
#3 OpenXcom -- is an open-source clone of #2 (https://openxcom.org/about/)
#4 OpenXcom Extended (OXCE) -- is a fork of #3 (https://openxcom.org/forum/index.php/topic,5251.0.html)

[aziza]

#2 there is no "Enemy Unknown (1994) Extended"

here is   ufopaedia.org/index.php/Enemy_Unknown_(1994)_Extended

[Meridian]

here is   ufopaedia.org/index.php/Enemy_Unknown_(1994)_Extended

That's just a guide how to install #2 + #1