Lol. he has that shit hosted through GoDaddy, why not just get his hosting termed. Personally if it were me, I'd email him and ask him to remove the software nicely first. If he doesn't respond, or attempts to be a smart ass and not help you, let him know that your first step will be to have his hosting terminated (there's no way GoDaddy allows uploading of cracked software and shit). If he attempts to rebuild the site, that hosting too will be terminated, and if it's not for some reason, the site will just be ddos'd offline until he responds accordingly. Make sure you can backup what you're saying, but a little googling can help you find everything you'd need to be able to do those things.
You'll screw him in 2 ways. For 1, it's obvious this clown makes like $1 a day type of money, so he can barely afford the hosting he has now probably, let alone having to continuously re-buy new hosting. If for some reason he's actually able to, a quick lil bump offline will usually grab someone's attention. You don't have to be an idiot and try and be all tough saying you're going to take him offline for days or anything, just knock him offline for an hour or so and email him a ss asking if he's reconsidered removing your piece of software, or the entire site if you prefer. At that point he's basically screwed. He won't be able to afford Cloudflare, and they won't host his garbage site anyway.
I'm not necessarily condoning this action by the way as it's definitely fighting fire with fire, and anything can happen then, but hypothetically, if someone were that upset about it, there are some "counter-measures" that can be taken. The ddos thing is dirty, and I really wouldn't recommend going that route unless all other options have been exhausted first though, if at all.