I hadn't heard of this move, but I think it's an inspired marketing move. For starters, it's a little like giving away the razor and selling the blades. KV331 has a large and ever growing number of sound banks all modestly priced (and some of them *very* good). It's easy to see how someone could try the starter for free or for nineteen bucks and end up coming back repeatedly for more sounds.
On top of that, it would be surprising if a fair percentage of the free-bee adopters didn't opt to spring for the full synth at some point once they started to appreciate the quality of this instrument. I'm a big fan of KV331 and wish them well on this.