VirtualEyez

VirtualEyez (was VirtualEyes) performs greenscreen removal for multiple cameras in real-time using the Mac's GPU (both chroma and luma keying).

The composited camera image (8-bit frame buffer with pre-multiplied alpha channel) is reflected to all clients of the VirtualEyez camera driver(s). Up to 3 cameras can be keyed in real-time with the output switched via keyboard control, mouse, or MIDI. Very low-latency output compatible with the new AVFoundation CMIO camera drivers. Also compatible with old QuickTime applications via the VDIG (video digitizer) driver.
Free vs. Paid: Starting with version 2.0, one channel of greenscreen functionality is included for free so you can fully explore the features of the app. Additional channels require a paid license. The leftmost (channel 0) channel should always be available. The middle and right channels (1 and 2) are only fully enabled when a valid license has been entered and activated.
DIY Greenscreen: We now recommend using compact flourescent bulbs. Incandescent bulbs which cast a more orange-hued light, consume more power and have less stable characteristics for lighting a greenscreen. For best results use "daylight bulbs" with a wide-spectrum, white output.