From the announcement:
Battlemage has been released! It is available at DriveThruRPG, Wargame Vault and RPGNow. There is a free version containing just the main rules available at all three of those links so you can have a look before buying; you can also buy individual sections ('modular' parts) without having to buy the full book. Although, at $5.99, it is cheaper to buy the full rules that all the sections individually!