Amplitube does the same thing. They give away the core program, but the gear models that make it useful must be bought in one of two ways:

1) you can buy them "a-la carte" at their online store or

2) you can buy packages like Amplitube FENDER, AMPEG, METAL etc and get a special interest combination of value adding content that is cheaper than buying all the same items one at a time at the web store.