The guy probably just wrote some code to generate randomly varying point spread functions, made a training data set by filtering a set of known images with the PSFs, and then training a neural net on the data. It's not a trivial task, but it's also not insanely difficult.
Like, the tool was made by one guy (I think?), so it can't be too difficult. It's more that most people don't have the technical skills to do it. I probably could (given sufficient time, which is the rub).