Please add a license for these. I'd love to use this in a game, but unless you say otherwise, you've reserved all rights.
The Hex Tileset he linked has "It's available under CC0 license.", so I'd imagine this tileset would be the same thing.
Unfortunately, that's not how licenses work. Unless the author says otherwise, each work is separately "all rights reserved".
It's available under CC BY 4.0, I added a note in the description.