The Star Cluster engine is a highly experimental large set of events that is used in Scirra Construct. It is mainly used in Epic Universe: Freedom, New Worlds 0.23 and onwards and the prototype Eternal Night. Basically, it was created to build a virtual universe, one that had multiple "factions" and "side factions" that interacted in real time. Unlike some other games, the universe built within the Star Cluster is real time, meaning events actually happen all at the same time, no matter where the player is and they actually exist, rather than only rendering around the player.

Not exactly. At least, not yet. Although the end result of this experimental engine will most likely be in the form of a plug-in, right now it is simply a large set of events that can be modified to create any open world game. At it's current state, it has to be directely implemented into a game built in Construct and modified to work with the new objects. On the other hand, simply by modifying certain variables, the behaviour of AI can be directly manipulated and empires be completely changed.

Not yet at the current stage of development. Star Cluster is still very much in experimental stages and is not finished, and also very much buggy. Once the engine has reached a usable and stable point, it will be available to the public for use as a Construct plug-in file.