It would be worthwhile to phrase this more constructively. They built something cool and they want to share it. The author is gaining nothing by posting this, and owes us nothing.
It's not the author's fault this was pushed to the frontpage of HN.
Neither is OP owes anything to author.
Sure, yes.
But, if you're trying to be a decent person you might want to encourage others to keep making cooling things rather than discourage them by saying "this free thing isn't good enough".
It's written in Java so...
that's just like the same thing as JavaScript, right?