ADClip3Demo is part of the ADClip development. In 2012, what ADClip was doing was working on incorporating the lessons learned from 3DClip, the one that adopted ‘energy redistribution’ techniques like Slate’s old FG-X. (ADClip4 still does this.) It soaks up clipped-off treble and bass energy, and works them back into the audio again where they’ll fit. This allows high-energy transients to hang on to some of their character.
ADClip3 came out with a single slider, which is a gain control from -3 to +24 db. It’s not as good at bypassing itself as ADClip4 is, so it has ‘a sound’ that may or may not suit you. As with all older versions, if it’s this one you want, buy the current version and ask for the older one, and I’ll send it along. As far as ADClip goes, I think it’s the current version you’ll want, but I’m not the boss of you :)