The DIY drivers will be commercially launched for under $50, writes developer CyberReality, who plans to launch alongside the imminent Rift development kits. Vireio (short for Virtual Reality Input Output) currently fully or partially supports just nine titles: Left 4 Dead, Half-Life 2, Portal 2, Skyrim, Mirror's Edge, AaaaAAaaAAA!!!, Unreal Tournament 3, Dear Esther and DiRT 2, with more planned to be added.
What makes these drivers unique is their ability to "pre-warp the image to match the Oculus Rift optics, handle custom aspect-ratios (needed for the Rift's strange 8:10 screen), and utilize full [three degrees of freedom] head-tracking".
It seems similar to how Nvidia's 3D Vision drivers jerry-rigged stereoscopic 3D support into old PC titles, with varying degrees of success. As work on the drivers continue, and as more titles are added, this could open up the possibility of Oculus Rift support for anything as far back as, erm, let's say Jet Set Willy.
The Oculus Rift itself was recently delayed by three months, with dev kits now expected to land in the laps of Kickstarter backers around mid-March.