ALAN (Adventure LANguage system) is developed by Thomas Nilsson and Göran Forslund. The ALAN pages at www.alanif.se provide a good starting point.
The ALAN authoring system consists of a compiler and an interpreter, both of which are available for the most common platforms -- Windows, MacOS and Linux. The source language is at a very high level, favouring description over traditional programmming.
Quoting from the FAQ for the rec.arts.int-fiction newsgroup, which was written when the current version of Alan was v2:
It isn't as powerful as the other Tier (i) systems. However, it is apparently easier to learn.
Read the complete ALAN entry at www.plover.net/~textfire/raiffaq/FAQ.htm#:ALAN (Adventure LANguage system) or the entire FAQ at www.plover.net/~textfire/raiffaq/.
The ALAN version of "Cloak of Darkness" was written by Stephen Griffiths (firstname.lastname@example.org), and converted to ALAN 3, the present version of the system, by Thomas Nilsson (email@example.com).