From the introduction:
These rules can be freely copied and amended. This allows users to record the changes they make to cover the needs of their particular campaign, and the extensions to the rules the make to handle situations the authors did not envisage or dismissed as unimportant. This recording can be done in a searchable form, by modifying the copy of the rules your campaign uses as authoritative, directly.
The document presents a robust skills system, flexible combat rules, and three magic systems. Additionally, everything needed for a fantasy roleplaying campaign is included.