Rules are standard 3.5 with the following adjustments:

Combat maneuvers.
The combat maneuver system from pathfinder is being implemented

All creatures have a combat maneuver bonus (CMB) and combat maneuver defense (CMD) these are used for resolving any kind of combat action that isn’t an attack, this includes Bull Rush, Dirty Tricks, Disarming, Dragging, Grappling, Overrunning, Stealing, Tripping and anything else that isn’t an attack or movement.

CMB = base attack bonus + Str modifier + special size modifier

CMD = 10 + base attack bonus + Str modifier + Dex modifier + special size modifier

Bonuses and penalties for size modifiers have been adjusted, the new values are:
Fine –16,
Diminutive –8,
Tiny –4,
Small –2,
Medium +0,
Large +2,
Huge +4,
Gargantuan +8,
Colossal +16.

This means that size has less of an effect in combat for small-medium-large creatures while remaining relevant for excessively large/small monsters.

Feats
Feats are now gained at every odd level.

Certain pathfinder feats will be allowed on a case by case basis, mostly ones that deal with Combat manoeuvres and the new skill system

Skills
Skills will be as per the pathfinder skill system:

New skill- Fly, this is used for any kind of aerial manoeuvrability, controlling skycabs, airships and soarsleds. You cannot take this skill without some kind of mundane or magical ability to fly or an appropriate feat.

Balance, Jump and tumble have been combined into Acrobatics
Gather information has been combined with Diplomacy
Open lock has been combined into Disable Device
Decipher Script and Forgery have been combined into Linguistics
Listen, Search and Spot have been combined into Perception
Hide and Move Silently have been combined into Stealth

Concentration is now a check for spellcasters, d20+caster level+primary casting stat
Use rope has been removed.