from the webpage:

Saga is a roleplaying engine I developed as a greatly simplified version of an earlier RPG that I no longer publish. It is a rules-light universal system with all the advantages and unique features of my previous system, but in greatly reduced form. Battle is deadly, non-combat characters and skills are important, magic is actually arcane and chaotic, and the emphasis is on realism and storytelling rather than stat keeping.

5th Edition contains a number of important system changes and improvements.