itch.io

You don't have to pay to contest it, all you do is dispute the claim, and they have 2 weeks (?) to file suit or it's dismissed. They have probably already filed a dispute.

A DMCA claim is an extra-judicial procedure, it's supposed to occur so everyone doesn't have to go to court (in theory). It's basically a fancy legal notice.

It seems like his package does not have a publisher signature (required to make your anti-virus not flag it). If you're using Windows you may need to click more information/continue. If you're using Mac you may be SoL.

You could also just download the source he linked in the video and build from that if you know how.