If all this is true it is really disturbing. Considering that we are in the process of sourcing out scripts right now I will probably give all of you a wide berth.
Personally if I were to buy a source script I would modify it if I considered it flawed or broken to the point that it was not working or a hazard to my system. I would do the same with any other software as well, license be damned.
Now if this guy is jacking your source then call your lawyer right now and shut him down. This will be easy enough to deal with.