There have been a multitude of SoftRocks, basically it's a project for people to sample SDR technology so it has been evolving as time moves on.

The basic principle is two direct conversion receivers using a FET switch as the mixer/down converter who are clocked at a 90 degree difference in phase (Quadrature) with the resulting two audio signals being generated as output, a PC using it's sound card to input the signals from the radio can control the received signal frequency, filter it, and detect the various modes.

The principle is keep the hardware simple and move common radio task to the computer software. It originally was a receiver only but as time moved on a transceiver was created.